Leetcode 312. Burst Balloons

 1 class Solution {
 2 public:
 3     int maxCoins(vector<int>& nums) {
 4         vector<int> arr;
 5         arr.push_back(1);
 6         for(int i:nums){
 7             arr.push_back(i);
 8         }
 9         arr.push_back(1);
10         vector<vector<int>> dp(arr.size(),vector<int>(arr.size(),-1));
11         return dfs(arr,0,arr.size()-1,dp);
12     }
13     
14     int dfs(vector<int> &arr, int left, int right, vector<vector<int>> &dp){
15         if(left+1==right) return 0;
16         if(dp[left][right]!=-1) return dp[left][right];    
17         int res=0;
18         for(int i=left+1;i<right;++i){
19             res=max(res,arr[left]*arr[i]*arr[right]+dfs(arr,left,i,dp)+dfs(arr,i,right,dp));
20         }
21         return dp[left][right]=res;
22     }
23 };