Create non_neg_int.py

Author: learning-zone

non_neg_int.py

@@ -0,0 +1,57 @@
+# Given an array arr of n unique non-negative integers, how can you most efficiently find a non-negative integer that is not in the array?
+
+# Your solution should return such an integer or null if arr contains all possible integers.
+# Analyze the runtime and space complexity of your solution.
+
+
+import sys
+
+
+def find_int(arr):
+    """ Takes an array and returns a non-negative integer that is not in the original array. Returns null if all integers are in the array.
+
+    Runtime: O(n)
+    Spacetime: O(n)
+
+    >>> find_int([0, 2, 1, 3, 4, 5, 11, 32, 42, 50, 100, 6])
+    7
+
+    >>> find_int([2, 4, 5, 1, 3])
+    0
+
+    >>> find_int([0, 2, 4, 5, 1, 3])
+    6
+
+    >>> find_int([0, 2, 4, 5, 1, 3, 6, 8])
+    7
+
+    >>> find_int([])
+    0
+
+    """
+
+    arr2 = {}
+
+    # If the length of the array is equal to the maximum allowed integers, there are no missing integers in the array.
+    if len(arr) == sys.maxint:
+        return None
+
+    # Create an O(1) lookup hashtable using the integers from the array as the key, and set the value to True
+    for i in range(len(arr)):
+        arr2[arr[i]] = True
+
+    # Loop through the length of the array + 1 and check if the number is a key in the hashtable. If it isn't return that number.
+    for i in range(len(arr) + 1):
+        if not arr2.get(i):
+            return i
+
+    return None
+
+
+if __name__ == '__main__':
+    import doctest
+    results = doctest.testmod()
+
+    if results.failed == 0:
+        print 'ALL TESTS PASSED!'
+