397. Integer Replacement

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

思路：

3是个特例，因为对于3来说，通过+1去掉2个1，不如-1

各种运算都要换成bit的才行，/2 %2之类的

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

res++;

}

return res;
}
}