Problem of The Day: Number Complement

1 min read 277 words

Problem Statement

leetcode problem link

Solution [accepted]

class Solution:
    def findComplement(self, num: int) -> int:
        res = num
        mask = 1
        while num > 0:
            res = res ^ mask
            mask <<= 1
            num >>= 1
        return res

public class Solution {
    public int FindComplement(int num) {
        int res = num;
        int temp = num;
        int mask = 1;
        while (temp > 0) {
            res ^= mask;
            mask <<= 1;
            temp >>= 1;
        }
        return res;
    }
}

Editorial

Approach 1: Flip Bit by Bit

class Solution:
    def findComplement(self, num):
        todo, bit = num, 1
        while todo:
            # flip the current bit
            num = num ^ bit

            # prepare for the next run
            bit = bit << 1
            todo = todo >> 1
        return num