題目：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
想到了要用位運算，但是有幾個要注意的點：
- 每個地方都要位運算防止超時‘
- 不要n++ 要 ++n
- +1和-1效果不一定相同，比如3（11）的-1效果更好
- 位運算每一步都要加括號
［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;
}
}
