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.
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.
Notice
m and n will be at most 100.
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;
if(m == 0 || n == 0) return 0;
int[][] dp = new int[m][n];
dp[0][0] = 1;
for(int i = 1; i < m; i++) {
for(int j = 1; j < n; j++) {
if(i * j == 0) {
dp[i][j] = 0;
}
}
}
for(int i = 0; i < m; i++) {
dp[i][0] = 1;
if(obstacleGrid[i][0] == 1) {
dp[i][0] = 0;
break;
}
}
for(int i = 0; i < n; i++) {
dp[0][i] = 1;
if(obstacleGrid[0][i] == 1) {
dp[0][i] = 0;
break;
}
}
for(int i = 1; i < m; i++) {
for(int j = 1; j < n; j++) {
if(obstacleGrid[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];
}
}