1. //从前往后，从里到外
    2. void getWinNum(vector<int> &arr){
    3.     if (arr.empty())return;
    4.     int len = arr.size();
    5.     vector<vector<int>> first(len, vector<int>(len, 0));
    6.     vector<vector<int>> second(len, vector<int>(len, 0));
    7.     for (int j = 0; j < len; ++j){
    8.         first[j][j] = arr[j];
    9.         for (int i = j - 1; i >= 0; --i){
    10.             first[i][j] = max(arr[i] + second[i + 1][j], arr[j] + second[i][j - 1]);
    11.             second[i][j] = min(first[i + 1][j], first[i][j - 1]);
    12.         }
    13.     }
    14.     cout << first[0][len - 1] << endl;
    15.     cout << second[0][len - 1] << endl;
    16. }
    17. //从后往前，从里到外
    18. void getWinNum(vector<int> &arr){
    19.     if (arr.empty())return;
    20.     int len = arr.size();
    21.     vector<vector<int>> first(len, vector<int>(len, 0));
    22.     vector<vector<int>> second(len, vector<int>(len, 0));
    23.     for (int i = 0; i < len; ++i)
    24.         first[i][i] = arr[i];
    25.     for (int i = len - 1; i >= 0; --i){
    26.         for (int j = i + 1; j < len; ++j){
    27.             first[i][j] = max(arr[i] + second[i + 1][j], arr[j] + second[i][j - 1]);
    28.             second[i][j] = min(first[i + 1][j], first[i][j - 1]);
    29.         }
    30.     }
    31.     cout << first[0][len - 1] << endl;
    32.     cout << second[0][len - 1] << endl;
    33. }