Sync LeetCode submission Runtime - 0 ms (100.00%), Memory - 17.9 MB (31.77%)

Author: jimit105

1646-kth-missing-positive-number/solution.py

@@ -1,18 +1,26 @@
 # Approach 2: Binary Search
 
-# Time: O(log N)
+# Time: O(log n)
 # Space: O(1)
 
 class Solution:
     def findKthPositive(self, arr: List[int], k: int) -> int:
         left, right = 0, len(arr) - 1
-
         while left <= right:
             pivot = (left + right) // 2
 
+            # If number of positive integers which are missing before arr[pivot] is less than k -->
+            # continue to search on the right.
             if arr[pivot] - pivot - 1 < k:
                 left = pivot + 1
             else:
                 right = pivot - 1
 
+        # At the end of the loop, left = right + 1,
+        # and the kth missing is in-between arr[right] and arr[left].
+        # The number of integers missing before arr[right] is
+        # arr[right] - right - 1 -->
+        # the number to return is
+        # arr[right] + k - (arr[right] - right - 1) = k + left
         return left + k
+