grid_unique_paths.cpp

#include<bits/stdc++.h>
using namespace std;

// Time comple - O(n * m);

class Solution {
public:
    int solve(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 = solve(i-1, j, dp);
        int left = solve(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));
        int ans = solve(m-1,n-1, dp);
        return ans;
        
    }
};