LeetCode 190 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 as 00111001011110000010100101000000).

Follow up:

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

第一次AC代码：

class Solution {public:    uint32_t reverseBits(uint32_t n) {        uint32_t ret=0;        int length=sizeof(n)*8;        for(int i=0,j=length-1;i<length;++i,--j){            ret+=(n&1)*pow(2,j);            n=n>>1;        }        return ret;    }};

第二次AC代码（参考了大神的代码）：

class Solution {public:    uint32_t reverseBits(uint32_t n) {        int length=sizeof(n)*8;        int ret=0;        for(int i=0;i<length;++i)            ret=(ret<<1)+(n>>i&1);        return ret;    }};