Unique Paths 1-2

int inner_path(int i, int j, int m, int n, vector<vector<int>>& record) {
    if (i < 0 || j < 0) {
        return 0;
    }

    if (record[i][j]) {
        return record[i][j];
    }

    if ((i == 0) && (j == 0)) {
        return 1;
    }

    record[i][j] = inner_path(i-1, j, m, n, record) + inner_path(i, j-1, m, n, record);
    return record[i][j];
}

int uniquePaths(int m, int n) {
    vector<vector<int>> res(m, vector<int>(n, 0));
    return inner_path(m-1, n-1, m, n, res);
}

int path_helper(int i, int j, int m, int n, vector<vector<int>>& record, vector<vector<int>> &obstacleGrid) {
        if (i < 0 || j < 0 || obstacleGrid[i][j] == 1) {
            return 0;
        }

        if (record[i][j]) {
            return record[i][j];
        }

        if ((i == 0) && (j == 0)) {
            return 1;
        }

        record[i][j] = path_helper(i - 1, j, m, n, record, obstacleGrid) + path_helper(i, j - 1, m, n, record, obstacleGrid);
        return record[i][j];
    }

    int uniquePathsWithObstacles(vector<vector<int>>& obstacleGrid) {
        if (obstacleGrid.empty()) return 0;
        int m = (int)obstacleGrid.size();
        int n = (int)obstacleGrid[0].size();

        vector<vector<int>> res(m, vector<int>(n, 0));
        return path_helper(m - 1, n - 1, m, n, res, obstacleGrid);
    }

int uniquePathsWithObstacles(vector<vector<int>>& grid) {
     int rows = grid.size();
     if(rows == 0) return 0;
     int cols = grid[0].size();
     vector<vector<long>> res(rows+1, vector<long>(cols+1, 0));
     for(int i=rows-1; i>=0;i--){
         for(int j=cols-1; j>=0;j--){
             if(grid[i][j] == 1) res[i][j] = 0;
             else if(i == rows-1 && j == cols-1) res[i][j] = 1;
             else res[i][j] = res[i][j+1] + res[i+1][j];
         }
     }
     return res[0][0];
 }