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.

5:101     6:110       7:111    4:100

从最高位开始相同的bits

int rangeBitwiseAnd(int m, int n) {

    //取第i位上的bit：(x>>i)&1
    //置n的每一位为1或者0：int n|=(1<<i) //即第i位置为1
    int i=0;
    while(m != n){
        m>>=1;//右移一位
        n>>=1;
        i++;
    }
    return m<<i;
}