Code

Solution of problem 476 is showed below. You can also find it here.

My solution

class Solution {
public:
    int findComplement(int num) {
        int ret = 0, cnt = 0;
        while(num) {
            ret |= ((num & 1) ^ 1) << cnt;
            num >>= 1;
            ++cnt;
        }
        return ret;
    }
};

A solution on Leetcode:

class Solution {
public:
    int findComplement(int num) {
        int mask = 1;
        while(mask < num)
            mask = (mask << 1) + 1;
        return num ^ mask;        
    }
};

Solution

This is a simple and easy problem. Just flip each bit and it’s all solved. You can iterate each bit or handle them all together.

Valueable Method

When seeing this kind of problem, I used to handle each bit and assemble them together. However, vectorize them (create a number and XOR with the original number) is a better way. Also, I ignore the feature that the all 1 bits sequence is the largest number at the sequence length.

Think more and code less all the time.