397. Integer Replacement

Medium (Trung bình) C++ 🔗 Xem trên LeetCode

📋 Đề Bài

Given a positive integer n, you can apply one of the following operations:

  1. If n is even, replace n with n / 2.
  2. If n is odd, replace n with either n + 1 or n - 1.

Return the minimum number of operations needed for n to become 1.

 

Example 1:

Input: n = 8
Output: 3
Explanation: 8 -> 4 -> 2 -> 1

Example 2:

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

Example 3:

Input: n = 4
Output: 2

 

Constraints:

  • 1 <= n <= 231 - 1

💻 Lời Giải

C++ 0397-integer-replacement.cpp 
class Solution {
public:
    int dp(int n) {
        if (n == INT_MAX) {
            return 32;
        }
        if (n == 1) {
            return 0;
        }
        if (n % 2 == 0) {
            return 1 + dp(n / 2);
        }
        return 1 + min(dp(n - 1), dp(n + 1));
    }
    
    int integerReplacement(int n) {
        return dp(n);
    }
};