[LeetCode 201] 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.

solution:

bit manipulation, calculate common 1 prefix between m and n;

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