Question
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.
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.
Stats
| Frequency | 3 |
| Difficulty | 3 |
| Adjusted Difficulty | 2 |
| Time to use | -------- |
Ratings/Color = 1(white) 2(lime) 3(yellow) 4/5(red)
Solution
This is similar question as previous one, but DP solution.
My code
public class Solution {
public int uniquePathsWithObstacles(int[][] obstacleGrid) {
int[][] ob = obstacleGrid;
if (ob == null || ob.length == 0) {
return 0;
}
int m = ob.length;
int n = ob[0].length;
int[][] dp = new int[m][n];
for (int i = 0; i < m; i++) {
for (int j = 0; j < n; j++) {
if (i == 0 && j == 0) {
dp[i][j] = ob[i][j] == 1 ? 0 : 1;
} else if (i == 0) {
dp[i][j] = dp[i][j - 1] * (ob[i][j] == 1 ? 0 : 1);
} else if (j == 0) {
dp[i][j] = dp[i - 1][j] * (ob[i][j] == 1 ? 0 : 1);
} else {
if (ob[i][j] == 1) {
dp[i][j] = 0;
} else {
dp[i][j] = dp[i - 1][j] + dp[i][j - 1];
}
}
}
}
return dp[m - 1][n - 1];
}
}