leetcode刷题记录--Number Complement

题目

难度：easy

Given a positive integer, output its complement number. The complement strategy is to flip the bits of its binary representation.

Note:
The given integer is guaranteed to fit within the range of a 32-bit signed integer.
You could assume no leading zero bit in the integer’s binary representation.
Example 1:

Input: 5
Output: 2
Explanation: The binary representation of 5 is 101 (no leading zero bits), and its complement is 010. So you need to output 2.

Example 2:

Input: 1
Output: 0
Explanation: The binary representation of 1 is 1 (no leading zero bits), and its complement is 0. So you need to output 0.
```
## 第一次解法

````javascript
/**
 * @param {number} num
 * @return {number}
 */
var findComplement = function(num) {
    let a = '';
    num.toString(2).split("").forEach(function(item){
        if(item === "1"){
            a += "0"
        }else{
            a += "1"
        }
    })
    return parseInt(a,2)
};
# runtime : 89 ms