Bitwise AND of Numbers Range

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.

这题如果按照题意做会超时，用移位的操作很妙，因为是并操作，其实只要最小的数和最大的数从左往右取相同的位即可。遇到不同就退出，因为他们中间肯定有数该为为0。

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

};