simple examples

src/extra_interview_problems/math_arrays_and_strings/find_largest_sum.py

@@ -0,0 +1,58 @@
+#!/usr/bin/python
+
+'''You are given an array of integers (both positive and negative). Find the contiguous
+sequence with the largest sum. Return the sum.'''
+
+
+def find_largest_sum(array):
+    '''
+    >>> find_largest_sum([-1, 2, -3, 5, 3, 1, -16, 7, 1, -13, 1])
+    9
+    >>> find_largest_sum([])
+    0
+    >>> find_largest_sum([1])
+    1
+    '''
+    if not array: return 0
+    p1, p2 = 0, 1
+    all_sums = set()
+    sum_ = array[p1]
+
+    while p1 < p2 and p2 < len(array):
+        if sum_ + array[p2] < 0:
+            all_sums.add(sum_)
+            p2 += 1
+            p1 = p2
+            sum_ = 0
+        sum_ += array[p2]
+        p2 += 1
+    all_sums.add(sum_)
+    return max(all_sums)
+
+
+
+def find_largest_sum_simple(array):
+    '''
+    >>> find_largest_sum_simple([-1, 2, -3, 5, 3, 1, -16, 7, 1, -13, 1])
+    9
+    >>> find_largest_sum_simple([])
+    0
+    >>> find_largest_sum_simple([1])
+    1
+    '''
+    max_sum, sum_ = 0, 0
+
+    for item in array:
+        sum_ += item
+        if max_sum < sum_:
+            max_sum = sum_
+        elif sum_ < 0:
+            sum_ = 0
+    return max_sum
+
+
+
+
+if __name__ == '__main__':
+    import doctest
+    doctest.testmod()

src/extra_interview_problems/math_arrays_and_strings/find_sum_ints.py

@@ -0,0 +1,35 @@
+#!/usr/bin/python
+
+'''Design an algorithm to find all pairs of integers within an array
+    which sum to a specified value.'''
+
+from collections import defaultdict
+
+def find_ints_sum(array, sum_):
+    '''
+    >>> find_ints_sum([4, 5, 3, 5, 2, 8, 1], 9)
+    set([(5, 4), (1, 8)])
+    >>> find_ints_sum([1, 2], 5)
+    set([])
+    >>> find_ints_sum([1], 1)
+    'Not enough values'
+    '''
+    if len(array)< 2:
+        return "Not enough values"
+
+    dict = defaultdict()
+    pairs = set()
+
+    for i in array:
+        if (sum_ - i) in dict:
+            pairs.add((i, sum_ -i))
+        else:
+            dict[i] = True
+
+    return pairs
+
+# if the array was sorted, we could do this with two pointers
+
+if __name__ == '__main__':
+    import doctest
+    doctest.testmod()