[leetcode][javascript]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?

之前对位操作不是很熟，经过这题有所理解。

js的符号位是挥之不去的，而当作位操作时，js的位操作限制在32位，除去一个符号位，其上限只能达到2^31 - 1，so，符号位上的数值需要单独计算

代码如下

/**
* @param {number} n - a positive integer
* @return {number} - a positive integer
*/
var reverseBits = function(n) {
var tmp ,res = 0;
var count = 1;
var sign = n&1;
n = n>>>1;
while(n){
tmp = n&1;
res = res|tmp<<(31-count);
++count;
n = n>>>1;
}
if(sign){
res +=2147483648;
}
return res;
};

然后顺便吐槽下，leetcode 的runtime在JS下没什么参考性，浮动好大。