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[leetcode]bitwise and of numbers range

admin 11月 11, 2020 0

题目描述

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.

 bin     dec
 101       5
 110       6

-------------
 100       4

再举一个例子

 bin      dec
 1000       8 
 1001       9
 1010       10
 1011       11
-------------
 1000       8

可以看出[m,n]范围内的书按位与的结果为m与n二进制表示左边（高位）的共同部分

代码

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