LeetCode Bitwise AND of Numbers Range

原题链接在这里:https://leetcode.com/problems/bitwise-and-of-numbers-range/

题目:

Given a range [m, n] where 0 <= m <= n <= 2147483647, return the bitwise AND of all numbers in this range, inclusive.

For example, given the range [5, 7], you should return 4.

题解:

举几个例子可以看出能位运算&出1 bit的位置都是高位,低位的所有可能数字走一遍都会是0. 

所以找m和n高位相同的1 bit, 后面都是0 bit.

Time Complexity: O(1), 最多32位. Space: O(1).

AC Java:

 1 public class Solution {
 2     public int rangeBitwiseAnd(int m, int n) {
 3         int count = 0;
 4         while(m!=n){
 5             m >>= 1;
 6             n >>= 1;
 7             count++;
 8         }
 9         return m <<= count;
10     }
11 }

 

posted @ 2015-10-29 10:55  Dylan_Java_NYC  阅读(206)  评论(0编辑  收藏  举报