[Python] Challenge 7 (ReadyToMerge)

challenge_7/python/mindm/README.md

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+# Challenge_7
+## Missing Number
+This method will find the missing number in O(1) space and O(n) time!
+Input is an unordered list from 0..n with 1 value missing.
+
+You can run tests with:
+```
+$ python3 test.py
+```

challenge_7/python/mindm/src/missing.py

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+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+
+
+def find_missing(input_list):
+    """ Find the missing number in shuffled list
+    """
+
+    # Mathematical formula for finding the sum of consequtive natural numbers
+    # (N*(N+1))/2
+    total = (len(input_list) * (len(input_list) +1)) / 2
+
+    summed = 0
+
+    for element in input_list:
+        summed += element
+
+    missing = total - summed
+
+    return missing

challenge_7/python/mindm/src/test.py

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+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+import unittest
+import random
+from missing import find_missing
+
+
+class TestDiff(unittest.TestCase):
+
+    def test_ordered(self):
+        self.assertEqual(find_missing([0,1,2,3,4,5,7]), 6)
+
+    def test_100_range(self):
+        big_range = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,
+            17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32,
+            33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48,
+            49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 65,
+            66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81,
+            82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97,
+            98, 99]
+        random.shuffle(big_range)
+        self.assertEqual(find_missing(big_range), 64)
+
+    def test_empty(self):
+        self.assertEqual(find_missing([]), 0)
+
+    def test_minimal(self):
+        self.assertEqual(find_missing([0]), 1)
+
+    def test_small_unordered(self):
+        self.assertEqual(find_missing([3,0,1]), 2)
+
+    def test_huge_range_shuffled(self):
+        huge_range = list(range(1000))
+        random.shuffle(list(huge_range))
+        missing = huge_range.pop(random.randint(0,999))
+        self.assertEqual(find_missing(huge_range), missing)
+
+
+if __name__ == '__main__':
+    unittest.main()