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:

public class Solution {
    public int rangeBitwiseAnd(int m, int n) {
        int count = 0;
        while(m!=n){
            m >>= 1;
            n >>= 1;
            count++;
        }
        return m <<= count;
    }
}