176.Reverse Bits

题目：

Reverse bits of a given 32 bits unsigned integer.

给定32位无符号整数的反转位。

Example:

Input: 43261596
Output: 964176192
Explanation: 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?

 如果多次调用此函数，您将如何优化它？

解答：

 1 public class Solution {
 2     // you need treat n as an unsigned value
 3     public int reverseBits(int n) {
 4         int res=0;
 5         for(int i=0;i<32;i++){
 6             if((n&1)==1)
 7                 res=(res<<1)+1;
 8             else
 9                 res=res<<1;
10             n=n>>1;
11         }
12         return res;
13     }
14 }

优化：

 1 public class Solution {
 2     // you need treat n as an unsigned value
 3     public int reverseBits(int n) {
 4         int res=0;
 5         for(int i=0;i<32;i++){
 6             res<<=1;
 7             if((n&1)==1) res++;
 8             n=n>>1;
 9         }
10         return res;
11     }
12 }

详解：

 

posted @ 2018-09-18 15:19  chan_ai_chao  阅读(90)  评论(0)  编辑  收藏  举报