不懂BitwiseANDofNumbersRange_201

https://leetcode.com/problems/bitwise-and-of-numbers-range/

lo

（图片来源https://leetcode.com/problems/bitwise-and-of-numbers-range/
）

留意下：

1. longest common prefix of all integer

public int rangeBitwiseAnd(int m, int n) {
      int i = 0; // i means we have how many bits are 0 on the right
      while(m != n){
        m >>= 1;
        n >>= 1;
        i++;  
      }  
      return m << i;  
    }


public int rangeBitwiseAnd1(int m, int n) {
        if (m == n){
            return m;
        }
        //The highest bit of 1 in diff is the highest changed bit. 得到不同的后几位
        int diff = m ^ n;
        //Index is the index of the highest changed bit. Starting at 1.  10进制转2进制位数
        int index = (int)(Math.log(diff) / Math.log(2)) + 1;
        //Eliminate the changed part.
        m = m >> index;
        return m << index;
    }