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 as00111001011110000010100101000000).

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

Related problem: Reverse Integer

题意：将十进制数值转换成二进制，将二进制字符串反转顺序，再转换成十进制，输出反转后的十进制数值。

/**
 * @param {number} n - a positive integer
 * @return {number} - a positive integer
 */
var reverseBits = function(n) {
    var cnt=n.toString(2);
    var res=cnt.split("").reverse().join("");
    var len=res.length;
    for(var i=0;i<32-len;i++){
        res+="0";
    }
    return parseInt(res,2);
};