LintCode : Unique Paths II

Problem Description:

Follow up for "Unique Paths":

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.

Code:

public class Solution {
/**
* @param obstacleGrid: A list of lists of integers
* @return: An integer
*/
public int uniquePathsWithObstacles(int[][] obstacleGrid) {
// write your code here
if (obstacleGrid == null || obstacleGrid.length == 0 || obstacleGrid[0].length == 0){
return 0;
}
int m = obstacleGrid.length;
int n = obstacleGrid[0].length;
int[][] paths = new int[m]
;

for (int i = 0; i < m; i++) {
if (obstacleGrid[i][0] == 0) {
paths[i][0] = 1;
} else {
break;
}
}

for (int i = 0; i < n; i++) {
if (obstacleGrid[0][i] == 0) {
paths[0][i] = 1;
} else {
break;
}
}

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

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

View Code
Hint:

Same as Unique Path, but you have to pay attention to situation where you can not get to there.