[LeetCode] 397. Integer Replacement

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

1. If n is even, replace n with n/2.
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

 

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코드

class Solution {
public:
    int integerReplacement(int n) {
        long int k{n};
        int cnt{0};
        while(k!=1){
            if(k == 3)
                return cnt + 2;
            if(k%2 == 1){
                if((k-1)/2 % 2 == 1)
                    k+=1;
                else
                    k-=1;
            }
            else
                k/=2;
            cnt++;
        }
        return cnt;
    }
};