[位运算]397. Integer Replacement

题目：397. Integer Replacement[Medium]

Given a positive integer n and you can do operations as follow:

If n is even, replace n with n/2.
If n is odd, you can replace n with either n + 1 or n - 1.
What is the minimum number of replacements needed for n to become 1?

Example 1:
Input:
8
Output:
3
Explanation:
8 -> 4 -> 2 -> 1
Example 2:
Input:
7
Output:
4
Explanation:
7 -> 8 -> 4 -> 2 -> 1
or
7 -> 6 -> 3 -> 2 -> 1

想到了要用位运算，但是有几个要注意的点：

1. 每个地方都要位运算防止超时‘
2. 不要n++ 要 ++n
3. +1和-1效果不一定相同，比如3（11）的-1效果更好
4. 位运算每一步都要加括号
   ［Runtime: 4 ms］

class Solution {
    public int integerReplacement(int n) {
        int count = 0;
        while(n>1){
             if((n & 1) == 1){
                 ++count;
                 if(n==3 || ((((n-1) >>>1) & 1) == 0)) --n;
                 else ++n;
             }
             n = n >>> 1;
             ++count;
        }
       return count;
        
    }
}