Solved find first missing number in an array

Problem1.cs

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+// Time Complexity : O(logn)
+// Space Complexity : O(1)
+// Did this code successfully run on Leetcode : Yes
+// Any problem you faced while coding this : No
+
+
+// Your code here along with comments explaining your approach
+
+/*
+I perform binary search on the sorted array to find the missing element. Each element from the missing element to the last element
+would differ from it's index by 2. If I find a middle element which satisfies the condition, I store the index and search on the left half
+as there might exist more elements that differ from the index by 2. 
+*/
+
+
+class Solution
+{
+    public int missingNumber(int[] arr)
+    {
+        // code here
+        int low = 0, high = arr.Length - 1;
+        int result = arr.Length;
+
+        while (low <= high)
+        {
+            int mid = low + (high - low) / 2;
+
+            if (arr[mid] - mid > 1)
+            {
+                result = mid;
+                high = mid - 1;
+            }
+
+            else
+            {
+                low = mid + 1;
+            }
+        }
+
+
+        return result + 1;
+    }
+}