[LeetCode]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.

思路：对[m,n]范围内所有的数取与，实际上最后结果就是m和n从最高前面有多少位同为1，然后把后面位全置零即可。

比如m=4;n=7

100&101&110=100  

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