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MY_BOOK/ebook_src/abstract_structures/HashTableClass.py

@@ -0,0 +1,41 @@
+#!/usr/bin/env python
+
+__author__ = "bt3"
+
+
+class HashTable(object):
+    def __init__(self, slots=10):
+        self.slots = slots
+        self.table = []
+        self.create_table()
+
+    def hash_key(self, value):
+        return hash(value)%self.slots
+
+    def create_table(self):
+        for i in range(self.slots):
+            self.table.append([])
+
+    def add_item(self, value):
+        key = self.hash_key(value)
+        self.table[key].append(value)
+
+    def print_table(self):
+        for key in range(len(self.table)):
+            print "Key is %s, value is %s." %(key, self.table[key])
+
+    def find_item(self, item):
+        pos = self.hash_key(item)
+        if item in self.table[pos]:
+            return True
+        else:
+            return False
+
+if __name__ == '__main__':
+    dic = HashTable(5)
+    for i in range(1, 40, 2):
+        dic.add_item(i)
+
+    dic.print_table()
+    assert(dic.find_item(20) == False)
+    assert(dic.find_item(21) == True)

MY_BOOK/ebook_src/abstract_structures/QueueClass.py

@@ -0,0 +1,47 @@
+#!/usr/bin/env python
+# Time: 5 min
+
+__author__ = "bt3"
+
+
+class Queue(object):
+    def __init__(self):
+        self.enq = []
+        self.deq = []
+
+    def enqueue(self, item):
+        return self.enq.append(item)
+
+    def deque(self):
+        if not self.deq:
+            while self.enq:
+                self.deq.append(self.enq.pop())
+        return self.deq.pop()
+
+    def peak(self):
+        if not self.deq:
+            while self.enq:
+                self.deq.append(self.enq.pop())
+        if self.deq:
+            return self.deq[-1]
+
+    def size(self):
+        return len(self.enq) + len(self.deq)
+
+    def isempty(self):
+        return not (self.enq + self.deq)
+
+if __name__ == '__main__':
+    q = Queue()
+    for i in range(1,11):
+        q.enqueue(i)
+    print 'Size:',  q.size()
+    print 'Is empty?', q.isempty()
+    print 'Peak: ', q.peak()
+    print
+    print 'Dequeuing...'
+    for i in range(10):
+        print q.deque()
+    print 'Size:',  q.size()
+    print 'Is empty?', q.isempty()
+    print 'Peak: ', q.peak()

MY_BOOK/ebook_src/abstract_structures/Stack.py

@@ -0,0 +1,63 @@
+#!/usr/bin/env python
+
+__author__ = "bt3"
+
+
+class Stack(object):
+    def __init__(self):
+        self.content = []
+        self.min_array = []
+        self.min = float('inf')
+
+    def push(self, value):
+        if value < self.min:
+            self.min = value
+
+        self.content.append(value)
+        self.min_array.append(self.min)
+
+    def pop(self):
+        if self.content:
+            value = self.content.pop()
+            self.min_array.pop()
+            if self.min_array:
+                self.min = self.min_array[-1]
+            return value
+        else:
+            return 'Empty List. '
+
+    def find_min(self):
+        if self.min_array:
+            return self.min_array[-1]
+        else:
+            return 'No min value for empty list.'
+
+    def size(self):
+        return len(self.content)
+
+    def isEmpty(self):
+        return not bool(self.content)
+
+    def peek(self):
+        if self.content:
+            return self.content[-1]
+        else:
+            print('Stack is empty.')
+
+
+    def __repr__(self):
+        return '{}'.format(self.content)
+
+
+if __name__ == '__main__':
+    q = Stack()
+
+    for i in range(15,20):
+        q.push(i)
+    for i in range(10,5,-1):
+        q.push(i)
+
+
+
+    for i in range(1, 13):
+        print q.pop(), q.find_min()

MY_BOOK/ebook_src/abstract_structures/__init__.py

@@ -0,0 +1 @@
+__all__=["hash_tables", "heap", "linked_list", "queues", "stacks"]

MY_BOOK/ebook_src/abstract_structures/heap/find_N_largest_smallest_items_seq.py

@@ -0,0 +1,51 @@
+#!/usr/bin/env python
+
+__author__ = "bt3"
+
+import heapq
+
+def find_N_largest_items_seq(seq, N):
+    ''' find the N largest items in a sequence '''
+    return heapq.nlargest(N,seq)
+
+def find_N_smallest_items_seq(seq, N):
+    ''' find the N smallest items in a sequence '''
+    return heapq.nsmallest(N, seq)
+
+def find_smallest_items_seq_heap(seq):
+    ''' find the smallest items in a sequence using heapify first'''
+    ''' heap[0] is always the smallest item '''
+    ''' pops the smallest item, O(logN) '''
+    heapq.heapify(seq)
+    return heapq.heappop(seq)
+
+def find_smallest_items_seq(seq):
+    '''  if it is only one item, min() is faster '''
+    return min(seq)
+
+def find_N_smallest_items_seq_sorted(seq, N):
+    '''  N ~ len(seq), better sort instead'''
+    return sorted(seq)[:N]
+
+def find_N_largest_items_seq_sorted(seq, N):
+    '''  N ~ len(seq), better sort instead'''
+    return sorted(seq)[len(seq)-N:]
+
+
+def test_find_N_largest_smallest_items_seq(module_name='this module'):
+    seq = [1, 3, 2, 8, 6, 10, 9]
+    N = 3
+    assert(find_N_largest_items_seq(seq, N) == [10, 9, 8])
+    assert(find_N_largest_items_seq_sorted(seq, N) == [8, 9, 10])
+    assert(find_N_smallest_items_seq(seq, N) == [1,2,3])
+    assert(find_N_smallest_items_seq_sorted(seq, N) == [1,2,3])
+    assert(find_smallest_items_seq(seq) == 1)
+    assert(find_smallest_items_seq_heap(seq) == 1)
+
+    s = 'Tests in {name} have {con}!'
+    print(s.format(name=module_name, con='passed'))
+
+
+if __name__ == '__main__':
+    test_find_N_largest_smallest_items_seq()
+

MY_BOOK/ebook_src/abstract_structures/heap/heapify.py

@@ -0,0 +1,49 @@
+#!/usr/bin/env python
+
+__author__ = "bt3"
+
+class Heapify(object):
+    def __init__(self, data=None):
+        self.data = data or []
+        for i in range(len(data)//2, -1, -1):
+            self.__max_heapify__(i)
+
+    def __repr__(self):
+        return '{}'.format(self.data)
+
+    def parent(self, i):
+        return i >> 1
+
+    def left_child(self, i):
+        return (i << 1) + 1
+
+    def right_child(self, i):
+        return (i << 1) + 2 # +2 instead of +1 because it's 0-indexed.
+
+    def __max_heapify__(self, i):
+        largest = i
+        left = self.left_child(i)
+        right = self.right_child(i)
+        n = len(self.data)
+        largest = (left < n and self.data[left] > self.data[i]) and left or i
+        largest = (right < n and self.data[right] > self.data[largest]) and right or largest
+        if i is not largest:
+            self.data[i], self.data[largest] = self.data[largest], self.data[i]
+            self.__max_heapify__(largest)
+
+    def extract_max(self):
+        n = len(self.data)
+        max_element = self.data[0]
+        self.data[0] = self.data[n - 1]
+        self.data = self.data[:n - 1]
+        self.__max_heapify__(0)
+        return max_element
+
+
+def test_Heapify():
+    l1 = [3, 2, 5, 1, 7, 8, 2]
+    h = Heapify(l1)
+    assert(h.extract_max() == 8)
+
+if __name__ == '__main__':
+    test_Heapify()

MY_BOOK/ebook_src/abstract_structures/heap/merge_sorted_seqs.py

@@ -0,0 +1,27 @@
+#!/usr/bin/env python
+
+__author__ = "bt3"
+
+import heapq
+
+
+def merge_sorted_seq(seq1, seq2):
+    ''' merge two sorted sequences with little ovehead. the result
+        will be sorted, which is different of doing just +'''
+    result = []
+    for c in heapq.merge(seq1, seq2):
+        result.append(c)
+    return result
+
+
+def test_merge_sorted_seq(module_name='this module'):
+    seq1 = [1, 2, 3, 8, 9, 10]
+    seq2 = [2, 3, 4, 5, 6, 7, 9]
+    seq3 = seq1 + seq2
+    assert(merge_sorted_seqseq1, seq2) == sorted(seq3))
+
+
+
+if __name__ == '__main__':
+    test_merge_sorted_seq()
+

MY_BOOK/ebook_src/abstract_structures/heap/priority_queue.py

@@ -0,0 +1,40 @@
+#!/usr/bin/env python
+
+__author__ = "bt3"
+
+import heapq
+
+class PriorityQueue(object):
+    ''' implements a priority queue class '''
+    def __init__(self):
+        self._queue = []
+        self._index = 0 # comparying same priority level
+
+    def push(self, item, priority):
+        heapq.heappush(self._queue, (-priority, self._index, item))
+        self._index += 1
+
+    def pop(self):
+        return heapq.heappop(self._queue)[-1]
+
+
+class Item:
+    def __init__(self, name):
+        self.name = name
+    def __repr__(self):
+        return "Item({!r})".format(self.name)
+
+
+def test_PriorityQueue():
+    ''' push and pop are all O(logN) '''
+    q = PriorityQueue()
+    q.push(Item('test1'), 1)
+    q.push(Item('test2'), 4)
+    q.push(Item('test3'), 3)
+    assert(str(q.pop()) == "Item('test2')")
+
+
+if __name__ == '__main__':
+    test_PriorityQueue()
+
+

MY_BOOK/ebook_src/abstract_structures/linked_list/circular_ll.py

@@ -0,0 +1,55 @@
+#!/usr/bin/env python
+
+__author__ = "bt3"
+
+
+''' implement a function to see whether a linked list is circular.
+    To implement this, we just need two pointers with different
+    paces (for example, one goes twice faster)'''
+
+from linked_list_fifo import LinkedListFIFO
+from node import Node
+
+
+class cicularLinkedListFIFO(LinkedListFIFO):
+    def _add(self, value):
+        self.length += 1
+        node = Node(value, self.head)
+        if self.tail:
+            self.tail.pointer = node
+        self.tail = node
+
+
+
+
+def isCircularll(ll):
+    p1 = ll.head
+    p2 = ll.head
+
+    while p2:
+        try:
+            p1 = p1.pointer
+            p2 = p2.pointer.pointer
+        except:
+            break
+
+        if p1 == p2:
+            return True
+    return False
+
+
+
+if __name__ == '__main__':
+
+    ll = LinkedListFIFO()
+    for i in range(10):
+        ll.addNode(i)
+    ll._printList()
+
+    print(isCircularll(ll))
+
+    lcirc = cicularLinkedListFIFO()
+    for i in range(10):
+        lcirc.addNode(i)
+    print(isCircularll(lcirc))
+

MY_BOOK/ebook_src/abstract_structures/linked_list/double_linked_list_fifo.py

@@ -0,0 +1,81 @@
+#!/usr/bin/env python
+
+__author__ = "bt3"
+
+''' Implement a double-linked list, which is very simple, we just need inherits
+from a Linked List Class and  add an attribute for previous.'''
+
+from linked_list_fifo import LinkedListFIFO
+
+
+class dNode(object):
+    def __init__(self, value=None, pointer=None, previous=None):
+        self.value = value
+        self.pointer = pointer
+        self.previous = previous
+
+
+class dLinkList(LinkedListFIFO):
+
+    def printListInverse(self):
+        node = self.tail
+        while node:
+            print(node.value)
+            try:
+                node = node.previous
+            except:
+                break
+
+    def _add(self, value):
+        self.length += 1
+        node = dNode(value)
+        if self.tail:
+            self.tail.pointer = node
+            node.previous = self.tail
+        self.tail = node
+
+    def _delete(self, node):
+        self.length -= 1
+        node.previous.pointer = node.pointer
+        if not node.pointer:
+            self.tail = node.previous
+
+    def _find(self, index):
+        node = self.head
+        i = 0
+        while node and i < index:
+            node = node.pointer
+            i += 1
+        return node, i
+
+    # delete nodes in general
+    def deleteNode(self, index):
+        if not self.head or not self.head.pointer:
+            self._deleteFirst()
+        else:
+            node, i = self._find(index)
+            if i == index:
+                self._delete(node)
+            else:
+                print('Node with index {} not found'.format(index))
+
+
+if __name__ == '__main__':
+
+    from collections import Counter
+
+    ll = dLinkList()
+    for i in range(1, 5):
+        ll.addNode(i)
+    print('Printing the list...')
+    ll._printList()
+    print('Now, printing the list inversely...')
+    ll.printListInverse()
+    print('The list after adding node with value 15')
+    ll._add(15)
+    ll._printList()
+    print("The list after deleting everything...")
+    for i in range(ll.length-1, -1, -1):
+        ll.deleteNode(i)
+    ll._printList()
+

MY_BOOK/ebook_src/abstract_structures/linked_list/find_kth_from_the_end.py

@@ -0,0 +1,42 @@
+#!/usr/bin/env python
+
+__author__ = "bt3"
+
+
+''' Find the mth-to-last element of a linked list.
+    One option is having two pointers, separated by m. P1 start at the roots
+    (p1 = self.root) and p2 is m-behinf pointer, which is created when p1 is at m.
+    When p1 reach the end, p2 is the node. '''
+
+from linked_list_fifo import LinkedListFIFO
+from node import Node
+
+
+class LinkedListFIFO_find_kth(LinkedListFIFO):
+
+
+    def find_kth_to_last(self, k):
+        p1, p2 = self.head, self.head
+        i = 0
+        while p1:
+            if i > k:
+                try:
+                    p2 = p2.pointer
+                except:
+                    break
+            p1 = p1.pointer
+            i += 1
+        return p2.value
+
+
+
+if __name__ == '__main__':
+    ll = LinkedListFIFO_find_kth()
+    for i in range(1, 11):
+        ll.addNode(i)
+    print('The Linked List:')
+    print(ll._printList())
+    k = 3
+    k_from_last = ll.find_kth_to_last(k)
+    print("The %dth element to the last of the LL of size %d is %d" %(k, ll.length, k_from_last))
+

MY_BOOK/ebook_src/abstract_structures/linked_list/linked_list_fifo.py

@@ -0,0 +1,90 @@
+#!/usr/bin/env python
+
+__author__ = "bt3"
+
+''' A class for a linked list that has the nodes in a FIFO order (such as a queue)'''
+
+
+from node import Node
+
+class LinkedListFIFO(object):
+
+    def __init__(self):
+        self.head = None
+        self.length = 0
+        self.tail = None # this is different from ll lifo
+
+    def _printList(self):
+        node = self.head
+        while node:
+            print(node.value)
+            node = node.pointer
+
+    def _addFirst(self, value):
+        self.length = 1
+        node = Node(value)
+        self.head = node
+        self.tail = node
+
+    def _deleteFirst(self):
+        self.length = 0
+        self.head = None
+        self.tail = None
+        print('The list is empty.')
+
+    def _add(self, value):
+        self.length += 1
+        node = Node(value)
+        if self.tail:
+            self.tail.pointer = node
+        self.tail = node
+
+    def addNode(self, value):
+        if not self.head:
+            self._addFirst(value)
+        else:
+            self._add(value)
+
+    def _find(self, index):
+        prev = None
+        node = self.head
+        i = 0
+        while node and i < index:
+            prev = node
+            node = node.pointer
+            i += 1
+        return node, prev, i
+
+    def deleteNode(self, index):
+        if not self.head or not self.head.pointer:
+            self._deleteFirst()
+        else:
+            node, prev, i = self._find(index)
+            if i == index and node:
+                self.length -= 1
+                if i == 0 or not prev :
+                    self.head = node.pointer
+                else:
+                    prev.pointer = node.pointer
+                if not self.tail == node:
+                    self.tail = prev
+            else:
+                print('Node with index {} not found'.format(index))
+
+
+if __name__ == '__main__':
+    ll = LinkedListFIFO()
+    for i in range(1, 5):
+        ll.addNode(i)
+    print('The list is:')
+    ll._printList()
+    print('The list after deleting node with index 2:')
+    ll.deleteNode(2)
+    ll._printList()
+    print('The list after adding node with value 15')
+    ll._add(15)
+    ll._printList()
+    print("The list after deleting everything...")
+    for i in range(ll.length-1, -1, -1):
+        ll.deleteNode(i)
+    ll._printList()

MY_BOOK/ebook_src/abstract_structures/linked_list/linked_list_lifo.py

@@ -0,0 +1,90 @@
+#!/usr/bin/env python
+
+__author__ = "bt3"
+
+
+''' Implement a unordered linked list, i.e. a LIFO linked list (like a stack) '''
+
+from node import Node
+
+class LinkedListLIFO(object):
+
+    def __init__(self):
+        self.head = None
+        self.length = 0
+
+    def _printList(self):
+        node = self.head
+        while node:
+            print(node.value)
+            node = node.pointer
+
+    def _delete(self, prev, node):
+        self.length -= 1
+        if not prev:
+            self.head = node.pointer
+        else:
+            prev.pointer = node.pointer
+
+    def _add(self, value):
+        self.length += 1
+        self.head = Node(value, self.head)
+
+    def _find(self, index):
+        prev = None
+        node = self.head
+        i = 0
+        while node and i < index:
+            prev = node
+            node = node.pointer
+            i += 1
+        return node, prev, i
+
+    def _find_by_value(self, value):
+        prev = None
+        node = self.head
+        found = 0
+        while node and not found:
+            if node.value == value:
+                found = True
+            else:
+                prev = node
+                node = node.pointer
+        return node, prev, found
+
+    def deleteNode(self, index):
+        node, prev, i = self._find(index)
+        if index == i:
+            self._delete(prev, node)
+        else:
+            print('Node with index {} not found'.format(index))
+
+    def deleteNodeByValue(self, value):
+        node, prev, found = self._find_by_value(value)
+        if found:
+            self._delete(prev, node)
+        else:
+            print('Node with value {} not found'.format(value))
+
+
+
+
+if __name__ == '__main__':
+    ll = LinkedListLIFO()
+    for i in range(1, 5):
+        ll._add(i)
+    print('The list is:')
+    ll._printList()
+    print('The list after deleting node with index 2:')
+    ll.deleteNode(2)
+    ll._printList()
+    print('The list after deleting node with value 3:')
+    ll.deleteNodeByValue(2)
+    ll._printList()
+    print('The list after adding node with value 15')
+    ll._add(15)
+    ll._printList()
+    print("The list after deleting everything...")
+    for i in range(ll.length-1, -1, -1):
+        ll.deleteNode(i)
+    ll._printList()

MY_BOOK/ebook_src/abstract_structures/linked_list/node.py

@@ -0,0 +1,33 @@
+#!/usr/bin/env python
+
+__author__ = "bt3"
+
+class Node(object):
+    def __init__(self, value=None, pointer=None):
+        self.value = value
+        self.pointer = pointer
+
+    def getData(self):
+        return self.value
+
+    def getNext(self):
+        return self.pointer
+
+    def setData(self, newdata):
+        self.value = newdata
+
+    def setNext(self, newpointer):
+        self.pointer = newpointer
+
+
+
+if __name__ == '__main__':
+    L = Node("a", Node("b", Node("c", Node("d"))))
+    assert(L.pointer.pointer.value=='c')
+
+    print(L.getData())
+    print(L.getNext().getData())
+    L.setData('aa')
+    L.setNext(Node('e'))
+    print(L.getData())
+    print(L.getNext().getData())

MY_BOOK/ebook_src/abstract_structures/linked_list/part_linked_list.py

@@ -0,0 +1,57 @@
+#!/usr/bin/env python
+
+__author__ = "bt3"
+
+''' This function divides a linked list in a value, where everything smaller than this value
+    goes to the front, and everything large goes to the back:'''
+
+
+from linked_list_fifo import LinkedListFIFO
+from node import Node
+
+
+def partList(ll, n):
+
+    more = LinkedListFIFO()
+    less = LinkedListFIFO()
+
+    node = ll.head
+
+    while node:
+        item = node.value
+
+        if item < n:
+            less.addNode(item)
+
+        elif item > n:
+            more.addNode(item)
+
+        node = node.pointer
+
+    less.addNode(n)
+    nodemore = more.head
+
+    while nodemore:
+        less.addNode(nodemore.value)
+        nodemore = nodemore.pointer
+
+    return less
+
+
+
+
+if __name__ == '__main__':
+
+    ll = LinkedListFIFO()
+    l = [6, 7, 3, 4, 9, 5, 1, 2, 8]
+    for i in l:
+        ll.addNode(i)
+
+    print('Before Part')
+    ll._printList()
+
+    print('After Part')
+    newll = partList(ll, 6)
+    newll._printList()
+
+

MY_BOOK/ebook_src/abstract_structures/linked_list/sum_linked_list.py

@@ -0,0 +1,85 @@
+#!/usr/bin/env python
+
+__author__ = "bt3"
+
+''' Supposing two linked lists representing numbers, such that in each of their
+    nodes they carry one digit. This function sums the two numbers that these
+    two linked lists represent, returning a third list representing the sum:'''
+
+
+from linked_list_fifo import LinkedListFIFO
+from node import Node
+
+
+class LinkedListFIFOYield(LinkedListFIFO):
+
+    # print each node's value, starting from the head
+    def _printList(self):
+        node = self.head
+        while node:
+            yield(node.value)
+            node = node.pointer
+
+
+
+def sumlls(l1, l2):
+
+    lsum = LinkedListFIFOYield()
+    dig1 = l1.head
+    dig2 = l2.head
+    pointer = 0
+
+    while dig1 and dig2:
+        d1 = dig1.value
+        d2 = dig2.value
+        sum_d = d1 + d2 + pointer
+        if sum_d > 9:
+            pointer = sum_d//10
+            lsum.addNode(sum_d%10)
+
+        else:
+            lsum.addNode(sum_d)
+            pointer = 0
+
+        dig1 = dig1.pointer
+        dig2 = dig2.pointer
+
+    if dig1:
+        sum_d = pointer + dig1.value
+        if sum_d > 9:
+            lsum.addNode(sum_d%10)
+        else:
+            lsum.addNode(sum_d)
+        dig1 = dig1.pointer
+
+    if dig2:
+        sum_d = pointer + dig2.value
+        if sum_d > 9:
+            lsum.addNode(sum_d%10)
+        else:
+            lsum.addNode(sum_d)
+        dig2 = dig2.pointer
+
+    return lsum
+
+
+
+
+
+
+if __name__ == '__main__':
+    l1 = LinkedListFIFOYield() # 2671
+    l1.addNode(1)
+    l1.addNode(7)
+    l1.addNode(6)
+    l1.addNode(2)
+
+    l2 = LinkedListFIFOYield() # 455
+    l2.addNode(5)
+    l2.addNode(5)
+    l2.addNode(4)
+
+    lsum = sumlls(l1, l2)
+    l = list(lsum._printList())
+    for i in reversed(l):
+        print i

MY_BOOK/ebook_src/abstract_structures/queues/animal_shelter.py

@@ -0,0 +1,109 @@
+#!/usr/bin/env python
+
+__author__ = "bt3"
+
+
+""" A class for an animal shelter with two queues"""
+
+
+class Node(object):
+    def __init__(self, animalName=None, animalKind=None, pointer=None):
+        self.animalName = animalName
+        self.animalKind = animalKind
+        self.pointer = pointer
+        self.timestamp = 0
+
+
+
+class AnimalShelter(object):
+    def __init__(self):
+        self.headCat = None
+        self.headDog = None
+        self.tailCat = None
+        self.tailDog = None
+        self.animalNumber = 0
+
+
+    # Queue any animal
+
+    def enqueue(self, animalName, animalKind):
+        self.animalNumber += 1
+        newAnimal = Node(animalName, animalKind)
+        newAnimal.timestamp = self.animalNumber
+
+        if animalKind == 'cat':
+            if not self.headCat:
+                self.headCat = newAnimal
+            if self.tailCat:
+                self.tailCat.pointer = newAnimal
+            self.tailCat = newAnimal
+
+        elif animalKind == 'dog':
+            if not self.headDog:
+                self.headDog = newAnimal
+            if self.tailDog:
+                self.tailDog.pointer = newAnimal
+            self.tailDog = newAnimal
+
+
+    # Dequeue methods
+
+    def dequeueDog(self):
+        if self.headDog:
+            newAnimal = self.headDog
+            self.headDog = newAnimal.pointer
+            return str(newAnimal.animalName)
+        else:
+            return 'No Dogs!'
+
+
+    def dequeueCat(self):
+        if self.headCat:
+            newAnimal = self.headCat
+            self.headCat = newAnimal.pointer
+            return str(newAnimal.animalName)
+        else:
+            return 'No Cats!'
+
+
+    def dequeueAny(self):
+        if self.headCat and not self.headDog:
+            return self.dequeueCat()
+        elif self.headDog and not self.headCat:
+            return self.dequeueDog()
+        elif self.headDog and self.headCat:
+            if self.headDog.timestamp < self.headCat.timestamp:
+                return self.dequeueDog()
+            else:
+                return self.dequeueCat()
+        else:
+            return ('No Animals!')
+
+
+
+    def _print(self):
+        print("Cats:")
+        cats = self.headCat
+        while cats:
+            print(cats.animalName, cats.animalKind)
+            cats = cats.pointer
+        print("Dogs:")
+        dogs = self.headDog
+        while dogs:
+            print(dogs.animalName, dogs.animalKind)
+            dogs = dogs.pointer
+
+
+if __name__ == '__main__':
+
+    qs = AnimalShelter()
+    qs.enqueue('bob', 'cat')
+    qs.enqueue('mia', 'cat')
+    qs.enqueue('yoda', 'dog')
+    qs.enqueue('wolf', 'dog')
+    qs._print()
+
+    print("Deque one dog and one cat...")
+    qs.dequeueDog()
+    qs.dequeueCat()
+    qs._print()

MY_BOOK/ebook_src/abstract_structures/queues/deque.py

@@ -0,0 +1,39 @@
+#!/usr/bin/env python
+
+__author__ = "bt3"
+
+''' a class for a double ended queue (also inefficient) '''
+
+from queue import Queue
+
+class Deque(Queue):
+
+    def enqueue_back(self, item):
+        self.items.append(item)
+
+    def dequeue_front(self):
+        return self.items.pop(0)
+
+
+
+if __name__ == '__main__':
+    queue = Deque()
+    print("Is the queue empty? ", queue.isEmpty())
+    print("Adding 0 to 10 in the queue...")
+    for i in range(10):
+        queue.enqueue(i)
+    print("Queue size: ", queue.size())
+    print("Queue peek : ", queue.peek())
+    print("Dequeue...", queue.dequeue())
+    print("Queue peek: ", queue.peek())
+    print("Is the queue empty? ", queue.isEmpty())
+    print(queue)
+
+    print("\nNow using the dequeue methods...")
+    print("Dequeue from front...", queue.dequeue_front())
+    print("Queue peek: ", queue.peek())
+    print(queue)
+    print("Queue from back...")
+    queue.enqueue_back(50)
+    print("Queue peek: ", queue.peek())
+    print(queue)

MY_BOOK/ebook_src/abstract_structures/queues/linked_queue.py

@@ -0,0 +1,80 @@
+#!/usr/bin/env python
+
+__author__ = "bt3"
+
+''' Queue acts as a container for nodes (objects) that are inserted and removed according FIFO'''
+
+
+class Node(object):
+    def __init__(self, value=None, pointer=None):
+        self.value = value
+        self.pointer = None
+
+
+class LinkedQueue(object):
+    def __init__(self):
+        self.head = None
+        self.tail = None
+
+
+    def isEmpty(self):
+        return not bool(self.head)
+
+
+    def dequeue(self):
+        if self.head:
+            value = self.head.value
+            self.head = self.head.pointer
+            return value
+        else:
+            print('Queue is empty, cannot dequeue.')
+
+
+    def enqueue(self, value):
+        node = Node(value)
+        if not self.head:
+            self.head = node
+            self.tail = node
+        else:
+            if self.tail:
+                self.tail.pointer = node
+            self.tail = node
+
+
+    def size(self):
+        node = self.head
+        num_nodes = 0
+        while node:
+                num_nodes += 1
+                node = node.pointer
+        return num_nodes
+
+
+    def peek(self):
+        return self.head.value
+
+
+    def _print(self):
+        node = self.head
+        while node:
+            print(node.value)
+            node = node.pointer
+
+
+
+
+if __name__ == '__main__':
+    queue = LinkedQueue()
+    print("Is the queue empty? ", queue.isEmpty())
+    print("Adding 0 to 10 in the queue...")
+    for i in range(10):
+        queue.enqueue(i)
+    print("Is the queue empty? ", queue.isEmpty())
+    queue._print()
+
+    print("Queue size: ", queue.size())
+    print("Queue peek : ", queue.peek())
+    print("Dequeue...", queue.dequeue())
+    print("Queue peek: ", queue.peek())
+    queue._print()
+

MY_BOOK/ebook_src/abstract_structures/queues/palindrome_checker_with_deque.py

@@ -0,0 +1,47 @@
+#!/usr/bin/env python
+
+__author__ = "bt3"
+
+
+""" Using our deque class and Python's deque class """
+
+
+import string
+import collections
+
+from deque import Deque
+
+
+STRIP = string.whitespace + string.punctuation + "\"'"
+
+def palindrome_checker_with_deque(str1):
+
+    d1 = Deque()
+    d2 = collections.deque()
+
+    for s in str1.lower():
+        if s not in STRIP:
+            d2.append(s)
+            d1.enqueue(s)
+
+
+    eq1 = True
+    while d1.size() > 1 and eq1:
+        if d1.dequeue_front() != d1.dequeue():
+            eq1 = False
+
+    eq2 = True
+    while len(d2) > 1 and eq2:
+        if d2.pop() != d2.popleft():
+            eq2 = False
+
+    return eq1, eq2
+
+
+
+
+if __name__ == '__main__':
+    str1 = 'Madam Im Adam'
+    str2 = 'Buffy is a Slayer'
+    print(palindrome_checker_with_deque(str1))
+    print(palindrome_checker_with_deque(str2))

MY_BOOK/ebook_src/abstract_structures/queues/queue.py

@@ -0,0 +1,63 @@
+#!/usr/bin/env python
+
+__author__ = "bt3"
+
+
+class Queue(object):
+
+    def __init__(self):
+        self.in_stack = []
+        self.out_stack = []
+
+    def _transfer(self):
+        while self.in_stack:
+            self.out_stack.append(self.in_stack.pop())
+
+    def enqueue(self, item):
+        return self.in_stack.append(item)
+
+    def dequeue(self):
+        if not self.out_stack:
+            self._transfer()
+        if self.out_stack:
+            return self.out_stack.pop()
+        else:
+            return "Queue empty!"
+
+    def size(self):
+        return len(self.in_stack) + len(self.out_stack)
+
+    def peek(self):
+        if not self.out_stack:
+            self._transfer()
+        if self.out_stack:
+            return self.out_stack[-1]
+        else:
+            return "Queue empty!"
+
+    def __repr__(self):
+        if not self.out_stack:
+            self._transfer()
+        if self.out_stack:
+            return '{}'.format(self.out_stack)
+        else:
+            return "Queue empty!"
+
+    def isEmpty(self):
+        return not (bool(self.in_stack) or bool(self.out_stack))
+
+
+if __name__ == '__main__':
+    queue = Queue()
+    print("Is the queue empty? ", queue.isEmpty())
+    print("Adding 0 to 10 in the queue...")
+    for i in range(10):
+        queue.enqueue(i)
+    print("Queue size: ", queue.size())
+    print("Queue peek : ", queue.peek())
+    print("Dequeue...", queue.dequeue())
+    print("Queue peek: ", queue.peek())
+    print("Is the queue empty? ", queue.isEmpty())
+
+    print("Printing the queue...")
+    print(queue)

MY_BOOK/ebook_src/abstract_structures/stacks/dec2bin_with_stack.py

@@ -0,0 +1,30 @@
+#!/usr/bin/env python
+
+__author__ = "bt3"
+
+
+'''transform a decimal number to a binary number with a stack '''
+
+
+from stack import Stack
+
+def dec2bin_with_stack(decnum):
+
+    s = Stack()
+    str_aux = ''
+
+    while decnum > 0:
+        dig = decnum % 2
+        decnum = decnum//2
+        s.push(dig)
+
+    while not s.isEmpty():
+        str_aux += str(s.pop())
+
+    return str_aux
+
+
+
+if __name__ == '__main__':
+    decnum = 9
+    assert(dec2bin_with_stack(decnum) == '1001')

MY_BOOK/ebook_src/abstract_structures/stacks/linked_stack.py

@@ -0,0 +1,71 @@
+#!/usr/bin/env python
+
+__author__ = "bt3"
+
+
+""" A stack made of linked list"""
+
+
+class Node(object):
+    def __init__(self, value=None, pointer=None):
+        self.value = value
+        self.pointer = pointer
+
+
+class Stack(object):
+    def __init__(self):
+        self.head = None
+
+    def isEmpty(self):
+        return not bool(self.head)
+
+    def push(self, item):
+        self.head = Node(item, self.head)
+
+
+    def pop(self):
+        if self.head:
+            node = self.head
+            self.head = node.pointer
+            return node.value
+        else:
+            print('Stack is empty.')
+
+
+    def peek(self):
+        if self.head:
+            return self.head.value
+        else:
+            print('Stack is empty.')
+
+
+    def size(self):
+        node = self.head
+        count = 0
+        while node:
+            count +=1
+            node = node.pointer
+        return count
+
+
+    def _printList(self):
+        node = self.head
+        while node:
+            print(node.value)
+            node = node.pointer
+
+
+
+if __name__ == '__main__':
+    stack = Stack()
+    print("Is the stack empty? ", stack.isEmpty())
+    print("Adding 0 to 10 in the stack...")
+    for i in range(10):
+        stack.push(i)
+    stack._printList()
+    print("Stack size: ", stack.size())
+    print("Stack peek : ", stack.peek())
+    print("Pop...", stack.pop())
+    print("Stack peek: ", stack.peek())
+    print("Is the stack empty? ", stack.isEmpty())
+    stack._printList()

MY_BOOK/ebook_src/abstract_structures/stacks/reverse_string_with_stack.py

@@ -0,0 +1,31 @@
+#!/usr/bin/env python
+
+__author__ = "bt3"
+
+
+''' Uses a stack to reverse a string '''
+
+from stack import Stack
+
+def reverse_string_with_stack(str1):
+
+  s = Stack()
+  revStr = ''
+
+  for c in str1:
+    s.push(c)
+
+  while not s.isEmpty():
+    revStr += s.pop()
+
+  return revStr
+
+
+
+if __name__ == '__main__':
+  str1 = 'Buffy is a Slayer!'
+  print(str1)
+  print(reverse_string_with_stack(str1))
+
+
+

MY_BOOK/ebook_src/abstract_structures/stacks/set_of_stacks.py

@@ -0,0 +1,56 @@
+#!/usr/bin/env python
+
+__author__ = "bt3"
+
+""" define a class for a set of stacks """
+
+from stack import Stack
+
+class SetOfStacks(Stack):
+    def __init__(self, capacity=4):
+        self.setofstacks = []
+        self.items = []
+        self.capacity = capacity
+
+
+    def push(self, value):
+        if self.size() >= self.capacity:
+            self.setofstacks.append(self.items)
+            self.items = []
+        self.items.append(value)
+
+
+    def pop(self):
+        value = self.items.pop()
+        if self.isEmpty() and self.setofstacks:
+            self.items = self.setofstacks.pop()
+        return value
+
+
+    def sizeStack(self):
+        return len(self.setofstacks)*self.capacity + self.size()
+
+
+    def __repr__(self):
+        aux = []
+        for s in self.setofstacks:
+             aux.extend(s)
+        aux.extend(self.items)
+        return '{}'.format(aux)
+
+
+
+if __name__ == '__main__':
+    capacity = 5
+    stack = SetOfStacks(capacity)
+    print("Is the stack empty? ", stack.isEmpty())
+    print("Adding 0 to 10 in the stack...")
+    for i in range(10):
+        stack.push(i)
+    print(stack)
+    print("Stack size: ", stack.sizeStack())
+    print("Stack peek : ", stack.peek())
+    print("Pop...", stack.pop())
+    print("Stack peek: ", stack.peek())
+    print("Is the stack empty? ", stack.isEmpty())
+    print(stack)

MY_BOOK/ebook_src/abstract_structures/stacks/stack.py

@@ -0,0 +1,65 @@
+#!/usr/bin/env python
+
+# copy of the class ../Stack.py
+
+__author__ = "bt3"
+
+
+class Stack(object):
+    def __init__(self):
+        self.content = []
+        self.min_array = []
+        self.min = float('inf')
+
+    def push(self, value):
+        if value < self.min:
+            self.min = value
+
+        self.content.append(value)
+        self.min_array.append(self.min)
+
+    def pop(self):
+        if self.content:
+            value = self.content.pop()
+            self.min_array.pop()
+            if self.min_array:
+                self.min = self.min_array[-1]
+            return value
+        else:
+            return 'Empty List. '
+
+    def find_min(self):
+        if self.min_array:
+            return self.min_array[-1]
+        else:
+            return 'No min value for empty list.'
+
+    def size(self):
+        return len(self.content)
+
+    def isEmpty(self):
+        return not bool(self.content)
+
+    def peek(self):
+        if self.content:
+            return self.content[-1]
+        else:
+            print('Stack is empty.')
+
+
+    def __repr__(self):
+        return '{}'.format(self.content)
+
+
+if __name__ == '__main__':
+    q = Stack()
+
+    for i in range(15,20):
+        q.push(i)
+    for i in range(10,5,-1):
+        q.push(i)
+
+
+
+    for i in range(1, 13):
+        print q.pop(), q.find_min()

MY_BOOK/ebook_src/abstract_structures/stacks/stack_with_min.py

@@ -0,0 +1,77 @@
+#!/usr/bin/env python
+
+__author__ = "bt3"
+
+''' A stack with a minimum lookup '''
+
+from stack import Stack
+
+
+class NodeWithMin(object):
+    def __init__(self, value=None, minimum=None):
+        self.value = value
+        self.minimum = minimum
+
+
+class StackMin(Stack):
+    def __init__(self):
+        self.items = []
+        self.minimum = None
+
+
+    def push(self, value):
+        if self.isEmpty() or self.minimum > value:
+           self.minimum = value
+        self.items.append(NodeWithMin(value, self.minimum))
+
+
+    def peek(self):
+        return self.items[-1].value
+
+
+    def peekMinimum(self):
+        return self.items[-1].minimum
+
+
+    def pop(self):
+        item = self.items.pop()
+        if item:
+            if item.value == self.minimum:
+                self.minimum = self.peekMinimum()
+            return item.value
+        else:
+            print("Stack is empty.")
+
+    def __repr__(self):
+        aux = []
+        for i in self.items:
+            aux.append(i.value)
+        return '{}'.format(aux)
+
+
+
+if __name__ == '__main__':
+    stack = StackMin()
+    print("Is the stack empty? ", stack.isEmpty())
+    print("Adding 0 to 10 in the stack...")
+    for i in range(10,3, -1):
+        stack.push(i)
+    print(stack)
+
+    print("Stack size: ", stack.size())
+    print("Stack peek and peekMinimum : ", stack.peek(), stack.peekMinimum())
+    print("Pop...", stack.pop())
+    print("Stack peek and peekMinimum : ", stack.peek(), stack.peekMinimum())
+    print("Is the stack empty? ", stack.isEmpty())
+    print(stack)
+
+    for i in range(5, 1, -1):
+        stack.push(i)
+    print(stack)
+
+    print("Stack size: ", stack.size())
+    print("Stack peek and peekMinimum : ", stack.peek(), stack.peekMinimum())
+    print("Pop...", stack.pop())
+    print("Stack peek and peekMinimum : ", stack.peek(), stack.peekMinimum())
+    print("Is the stack empty? ", stack.isEmpty())
+    print(stack)

MY_BOOK/ebook_src/abstract_structures/stacks/towers_of_hanoi.py

@@ -0,0 +1,41 @@
+#!/usr/bin/env python
+
+__author__ = "bt3"
+
+
+
+""" Implement the 'towers of hanoi'"""
+
+from linked_stack import Stack, Node
+
+
+def moveTop(s1, s3):
+
+    s3.append(s1.pop())
+
+
+def moveDisks(n, s1, s3, s2):
+
+    if n < 1: return
+    moveDisks(n - 1, s1, s2, s3)
+    moveTop(s1, s3)
+    moveDisks(n -1, s2, s3, s1)
+
+
+
+def towersOfHanoi(n):
+    s1 = [x+1 for x in range(n)]
+    s2 = []
+    s3 = []
+    print('The first stick is {0} and the third stick has {1}'.format(s1, s3))
+
+    moveDisks(n, s1, s3, s2)
+
+    print('The first stick is {0} and the third stick has {1}'.format(s1, s3))
+
+    return s3
+
+
+
+if __name__ == '__main__':
+    towersOfHanoi(6)