Min Sum Path in Triangle

• Time : $O(n^2)$
• Space : $O(n^2)$

int helper(vector<vector<int>>& A, vector<vector<int>>& dp, int r, int n, int c) {
    if(r == n) return 0;
    if(dp[r][c] != -1) return dp[r][c];
    return dp[r][c] = A[r][c] + min(helper(A,dp,r + 1, n, c), helper(A,dp,r + 1, n, c + 1));
}
int Solution::minimumTotal(vector<vector<int> > &A) {
    int n = A.size();
    vector<vector<int>> dp(n,vector<int>(n,-1));
    return helper(A,dp,0,n,0);
}