546. Remove Boxes(Leetcode每日一题-2020.08.15)--抄答案

Problem

Given several boxes with different colors represented by different positive numbers.
You may experience several rounds to remove boxes until there is no box left. Each time you can choose some continuous boxes with the same color (composed of k boxes, k >= 1), remove them and get k*k points.
Find the maximum points you can get.

Constraints:

• 1 <= boxes.length <= 100
• 1 <= boxes[i] <= 100

Example

Input: boxes = [1,3,2,2,2,3,4,3,1]
Output: 23
Explanation:
[1, 3, 2, 2, 2, 3, 4, 3, 1]
----> [1, 3, 3, 4, 3, 1] (33=9 points)
----> [1, 3, 3, 3, 1] (11=1 points)
----> [1, 1] (33=9 points)
----> [] (22=4 points)

Solution

class Solution {
public:
int dp[100][100][100];

int removeBoxes(vector& boxes) {
    memset(dp, 0, sizeof dp);
    return calculatePoints(boxes, 0, boxes.size() - 1, 0);
}

int calculatePoints(vector& boxes, int l, int r, int k) {
    if (l > r) return 0;
    if (dp[l][r][k] != 0) return dp[l][r][k];
    while (r > l && boxes[r] == boxes[r - 1]) {
        r--;
        k++;
    }
    dp[l][r][k] = calculatePoints(boxes, l, r - 1, 0) + (k + 1) * (k + 1);
    for (int i = l; i < r; i++) {
        if (boxes[i] == boxes[r]) {
            dp[l][r][k] = max(dp[l][r][k], calculatePoints(boxes, l, i, k + 1) + calculatePoints(boxes, i + 1, r - 1, 0));
        }
    }
    return dp[l][r][k];
}

};