```
public int uniquePathsWithObstacles(int[][] obstacleGrid) {
int m = obstacleGrid.length, n = obstacleGrid[0].length;
int[][] path = new int[m][n];
for (int i = 0; i < m; i++) {
if (obstacleGrid[i][0] == 1) {
path[i][0] = 0;
//on the first column, if there is an obstacle, the rest are blocked.
//no need to continue.
break;
} else
path[i][0] = 1;
}
for (int j = 0; j < n; j++) {
if (obstacleGrid[0][j] == 1) {
path[0][j] = 0;
//First row, once obstacle found, the rest are blocked.
break;
} else
path[0][j] = 1;
}
for (int i = 1; i < m; i++) {
for (int j = 1; j < n; j++) {
if (obstacleGrid[i][j] == 1)
path[i][j] = 0;
else
path[i][j] = path[i-1][j] + path[i][j-1];
}
}
return path[m-1][n-1];
}
```