Missing number problem

MissingNumber.py

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+# Time Complexity : O(log n)
+# Space Complexity : O(1)
+# Did this code successfully run on Leetcode : Yes
+# Any problem you faced while coding this : No
+# Approach : Use binary search to find the index where low and high indices cross each other. 
+
+class Solution:
+    def missingNumber(self, arr):
+
+        low, high = 0, len(arr) - 1
+
+        while low <= high:
+            mid = low + (high - low) // 2
+
+            if arr[mid] <= (mid + 1):
+                low = mid + 1
+            else:
+                high = mid - 1
+
+        return low + 1