# Unique Paths II

## Problem

Now consider if some obstacles are added to the grids. How many unique paths would there be?

An obstacle and empty space is marked as 1 and 0 respectively in the grid.

## Example

For example, There is one obstacle in the middle of a 3x3 grid as illustrated below.

[
[0,0,0],
[0,1,0],
[0,0,0]
]

The total number of unique paths is 2.

## Note

m and n will be at most 100.

## Code - Java

public class Solution {
/**
* @param obstacleGrid: A list of lists of integers
* @return: An integer
*/
public int uniquePathsWithObstacles(int[][] obstacleGrid) {
int m = obstacleGrid.length;
int n = obstacleGrid[0].length;
int[][] cnt = new int[m][n];
cnt[0][0] = 1;
for (int i = 0; i < m; i++) {
for (int j = 0; j < n; j++) {
if (i == 0 && j == 0 || obstacleGrid[i][j] == 1) {
continue;
}
cnt[i][j] = 0;
if (i - 1 >= 0 && cnt[i - 1][j] != 0 && obstacleGrid[i - 1][j] == 0) {
cnt[i][j] += cnt[i - 1][j];
}
if (j - 1 >= 0 && cnt[i][j - 1] != 0 && obstacleGrid[i][j - 1] == 0) {
cnt[i][j] += cnt[i][j - 1];
}
}
}
return cnt[m - 1][n - 1];
}
}