Easy to understand 2D dp solution!
Intuition\n Describe your first thoughts on how to solve this problem. \n\n# Approach\n Describe your approach to solving the problem. \n\n# Complexity\n- Time 
# Intuition\n<!-- Describe your first thoughts on how to solve this problem. -->\n\n# Approach\n<!-- Describe your approach to solving the problem. -->\n\n# Complexity\n- Time complexity:\n<!-- Add your time complexity here, e.g. $$O(n)$$ -->\n\n- Space complexity:\n<!-- Add your space complexity here, e.g. $$O(n)$$ -->\n\n# Code\n```cpp []\nclass Solution {\npublic:\nint help(int &k,int day,int city,vector<vector<int>>& ss, vector<vector<int>>& ts,vector<vector<int>> &dp){\n    if(day==k) return 0;\n    if(dp[day][city]!=-1) return dp[day][city];\n    int stay= ss[day][city]+help(k,day+1,city,ss,ts,dp);\n    int mx=-1;\n    for(int i=0;i<ts[city].size();i++){\n        mx=max(mx,ts[city][i]+help(k,day+1,i,ss,ts,dp));\n    }\n    return dp[day][city]=max(mx,stay);\n}\n    int maxScore(int n, int k, vector<vector<int>>& ss, vector<vector<int>>& ts) {\n        int mx=-1;\n        vector<vector<int>> dp(k,vector<int>(n,-1));\n        for(int i=0;i<n;i++){\n            mx=max(mx,help(k,0,i,ss,ts,dp));\n        }\n        return mx;\n    }\n};\n```
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