LeetCode 190: Reverse Bits

题目描述：

Reverse bits of a given 32 bits unsigned integer.

For example, given input 43261596 (represented in binary as 00000010100101000001111010011100), return 964176192 (represented in binary as00111001011110000010100101000000).

Follow up:
If this function is called many times, how would you optimize it?

思路：

主要考察位运算

1.result=0，result=result + 将数字和1做位与运算，对数字不停做位右移操作，直至数字为0；

2.将32位数字补全

    uint32_t reverseBits(uint32_t n) {
        uint32_t result;
        int num = 0;
        while(n){
            result = result *2 + (uint32_t)(n&1);
            n = n>>1;
            num++;
        }
        while(num<32){
            result = result<<1;
            num++;
        }
        return result;
    }