Complement of Base 10 Integer

Author: anantkaushik

1009-complement-of-base-10-integer.py

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+"""
+Problem Link: https://leetcode.com/problems/complement-of-base-10-integer/
+
+The complement of an integer is the integer you get when you flip all the 0's to 1's and all the 1's to 0's 
+in its binary representation.
+For example, The integer 5 is "101" in binary and its complement is "010" which is the integer 2.
+Given an integer n, return its complement.
+
+Example 1:
+Input: n = 5
+Output: 2
+Explanation: 5 is "101" in binary, with complement "010" in binary, which is 2 in base-10.
+
+Example 2:
+Input: n = 7
+Output: 0
+Explanation: 7 is "111" in binary, with complement "000" in binary, which is 0 in base-10.
+
+Example 3:
+Input: n = 10
+Output: 5
+Explanation: 10 is "1010" in binary, with complement "0101" in binary, which is 5 in base-10.
+ 
+Constraints:
+0 <= n < 109
+"""
+# Time Complexity: O(logN)
+class Solution:
+    def bitwiseComplement(self, n: int) -> int:
+        mask = 1
+        
+        """
+        (number) => (how-number-is-derived)=>binary-string
+        mask = 1 => 1 => 1
+        mask = 3 => (2*1 + 1) => 11
+        mask = 7 => (3*2 + 1) => 111
+        mask = 15 => (7*2 + 1) => 1111
+        """
+        while mask < n:
+            mask = mask * 2 + 1
+        
+        return mask ^ n