tag: DP

class Solution {
    public int uniquePathsWithObstacles(int[][] obstacleGrid) {
        if (obstacleGrid[0][0] == 1) return 0;
        int n = obstacleGrid.length, m = obstacleGrid[0].length;
        int[][] dp = new int[n][m];

        dp[0][0] = 1;
        for (int i = 1; i < n; i++){
            if (obstacleGrid[i][0] == 1){
                dp[i][0] = 0;
                continue;
            }
            else{
                dp[i][0] = obstacleGrid[i - 1][0] == 0 ? dp[i - 1][0] : 0;    
            }
        }

        for (int i = 1; i < m; i++){
            if (obstacleGrid[0][i] == 1){
                dp[0][i] = 0;
                continue;
            }
            else{
                dp[0][i] = obstacleGrid[0][i - 1] == 0 ? dp[0][i - 1] : 0;    
            }
        }

        for (int i = 1; i < n; i++){
            for (int j = 1; j < m; j++){
                if (obstacleGrid[i][j] == 1){
                    dp[i][j] = 0;
                    continue;
                }
                else{
                    dp[i][j] = dp[i - 1][j] + dp[i][j - 1];
                }
            }
        }

        return dp[n - 1][m - 1];
    }
}