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

Solution

public class Solution {
    public int integerReplacement(int n) {
        if(n <= 0) return -1;
        if(n == Integer.MAX_VALUE) return 32;
        int cnt = 0;
        while(n != 1) {
            cnt ++;
            if(n % 2 == 0) {
                n >>= 1;
            } else {
                if( n != 3 && ((n >> 1) & 1) != 0  ) {
                    // multiple 1
                    n++;
                } else {
                    n--;   
                }
            }
        }
        return cnt;
    }
}