cleaning up and organizing old problems (builtin)

src/builtin_structures/interserction_two_arrays.py

@@ -0,0 +1,63 @@
+#!/usr/bin/env python
+
+__author__ = "bt3"
+
+
+def intersection_two_arrays_sets(seq1, seq2):
+    '''
+    >>> intersection_two_arrays_sets([1,2,3,5,7,8], [3,5,6])
+    set([3, 5])
+    >>> intersection_two_arrays_sets([1,2,7,8], [3,5,6])
+    set([])
+    '''
+    # O(n)
+    set1 = set(seq1)
+    set2 = set(seq2)
+
+    return set1.intersection(set2)  #same as list(set1 & set2)
+
+
+def intersection_two_arrays_On2(seq1, seq2):
+    '''
+    >>> intersection_two_arrays_On2([1,2,3,5,7,8], [3,5,6])
+    [3, 5]
+    >>> intersection_two_arrays_On2([1,2,7,8], [3,5,6])
+    []
+    '''
+
+    final = []
+
+    for i in seq1:
+        for j in seq2:
+            if i == j:
+                final.append(i)
+
+    return final
+
+
+def intersection_two_arrays_On(seq1, seq2):
+    '''
+    >>> intersection_two_arrays_On([1,2,3,5,7,8], [3,5,6])
+    [5, 3]
+    >>> intersection_two_arrays_On([1,2,7,8], [3,5,6])
+    []
+    '''
+
+    final = []
+
+    while seq1 and seq2:
+
+        if seq1[-1] == seq2[-1]:
+            final.append(seq1.pop())
+            seq2.pop()
+        elif seq1[-1] > seq2[-1]:
+            seq1.pop()
+        else:
+            seq2.pop()
+
+    return final
+
+
+if __name__ == '__main__':
+    import doctest
+    doctest.testmod()