unique_paths_2.cpp

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

// problem : https://leetcode.com/problems/unique-paths-ii

class Solution {
public:
    int uniquePathsWithObstacles(vector<vector<int>>& obstacleGrid) {
        int n=obstacleGrid.size(),m=obstacleGrid[0].size();
        vector<vector<int>>dp(n,vector<int>(m,1));
        int f=0;
        for(int i=0;i<n;i++){
            if(obstacleGrid[i][0] == 1){
                f = 1;
            }
            if(f == 1){
                dp[i][0] = 0;
            }
        }
        f=0;
        for(int i=0;i<m;i++){
            if(obstacleGrid[0][i] == 1){
                f = 1;
            }
            if(f == 1){
                dp[0][i] = 0;
            }
        }
        for(int i=1;i<n;i++){
            for(int j=1;j<m;j++){
                if(obstacleGrid[i][j] == 0){
                    dp[i][j] = dp[i-1][j] + dp[i][j-1];
                }
                else{
                    dp[i][j] = 0;
                }
            }
        }
        return dp[n-1][m-1];
    }
};