Reverse Bits

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?

Related problem: Reverse Integer

Credits:
Special thanks to @ts for adding this problem and creating all test cases.

代码：

class Solution {
public:
    uint32_t reverseBits(uint32_t n) {
        bitset<32> vec;
        int num=31;
        while(num>=0){
            uint32_t temp=n&1;
            vec[num]=temp;
            n=n>>1;
            --num;
        }
        uint32_t res=0;
        for(uint32_t i=0;i<32;++i){
            if(vec[i]==1) res+=pow(2,i);
        }
        return res;
    }
};