leetcode--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

[java]  view plain  copy

1. public class Solution {  
2.     // you need treat n as an unsigned value  
3.     public int reverseBits(int n) {  
4.         for(int i=0;i<16;i++){  
5.             n = swap(n, i, 31-i);  
6.         }  
7.         return n;  
8.     }  
9.       
10.     /** 
11.      * 交换imj位 
12.      * @param n 
13.      * @param i 
14.      * @param j 
15.      * @return 
16.      */  
17.     int swap(int n,int i,int j){  
18.         int t = (n>>i)&1;//获取第i位        
19.         n = n&(~(1<<i));//将第i位置0        
20.         int t2 = (n>>j)&1;//获取第j为  
21.         n = n&(~(1<<j));//将第j位置0        
22.         n = n|(t<<j);//将第j位设置为原i位上的数        
23.         n = n|(t2<<i);//将第i位设置为原j位上的数  
24.         return n;  
25.     }  
26. }  

原文链接http://blog.youkuaiyun.com/crazy__chen/article/details/45440747