lec10_18.cpp

class Solution {
    public: 
        int f(int i ,int  j,vector<vector<int>>&dp){
            if(i == 0 && j == 0) return 1;
            if(i<0 || j<0) return 0 ;
            if( dp[i][j]!= -1) return dp[i][j];
            int up = f(i-1, j, dp);
            int left = f(i , j-1,dp);
    
            return dp[i][j] = up+left;
        }
        int uniquePaths(int m, int n) {
            vector<vector<int>>dp( m , vector<int>(n,-1));
            return f(m-1, n-1,dp);
        }
    };