20-8-24 Stone Game II.cpp

class Solution {
public:
    int stoneGameII(vector<int>& piles) {
        int length = piles.size();
        vector<vector<int>>dp(length + 1, vector<int>(length + 1,0));
        vector<int> sufsum (length + 1, 0);
        for (int i = length - 1; i >= 0; i--) {
            sufsum[i] = sufsum[i + 1] + piles[i];
        }
        for (int i = 0; i <= length; i++) {
            dp[i][length] = sufsum[i];
        }
        for (int i = length - 1; i >= 0; i--) {
            for (int j = length - 1; j >= 1; j--) {
                for (int X = 1; X <= 2 * j && i + X <= length; X++) {
                    dp[i][j] = max(dp[i][j], sufsum[i] - dp[i + X][max(j, X)]);
                }
            }
        }
        return dp[0][1];
    }
};