[LeetCode] 651. 4 Keys Keyboard 四键的键盘

2021年09月15日 阅读数:1
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Imagine you have a special keyboard with the following keys:html

Key 1: (A): Print one 'A' on screen.app

Key 2: (Ctrl-A): Select the whole screen.post

Key 3: (Ctrl-C): Copy selection to buffer.url

Key 4: (Ctrl-V): Print buffer on screen appending it after what has already been printed.code

Now, you can only press the keyboard for N times (with the above four keys), find out the maximum numbers of 'A' you can print on screen.htm

Example 1:blog

Input: N = 3
Output: 3
Explanation: 
We can at most get 3 A's on screen by pressing following key sequence:
A, A, A

Example 2:ci

Input: N = 7
Output: 9
Explanation: 
We can at most get 9 A's on screen by pressing following key sequence:
A, A, A, Ctrl A, Ctrl C, Ctrl V, Ctrl V

Note:get

  1. 1 <= N <= 50
  2. Answers will be in the range of 32-bit signed integer.

 

 C++:it

class Solution {
public:
    int maxA(int N) {
        int res = N;
        for (int i = 1; i < N - 2; ++i) {
            res = max(res, maxA(i) * (N - 1 - i));
        }
        return res;
    }
};

C++:

 class Solution {
public:
    int maxA(int N) {
        vector<int> dp(N + 1, 0);
        for (int i = 0; i <= N; ++i) {
            dp[i] = i;
            for (int j = 1; j < i - 2; ++j) {
                dp[i] = max(dp[i], dp[j] * (i - j - 1));
            }
        }
        return dp[N];
    }
};

  

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