[Leetcode] Unique Paths II (Java)

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.

DP：

1)若obstacleGrid[i][j]=1,则dp[i][j]=0;

2)若obstacleGrid[i][j]=0,则dp[i][j]=d[i-1][j]+dp[i][j-1];

public class Solution {
public int uniquePathsWithObstacles(int[][] obstacleGrid) {
if(obstacleGrid.length<1)
return 0;
int dp[][]=new int[obstacleGrid.length][obstacleGrid[0].length];

dp[0][0]=obstacleGrid[0][0]==1?0:1;

for(int i=1;i<obstacleGrid.length;i++){
if(obstacleGrid[i][0]==1)
dp[i][0]=0;
else
dp[i][0]=dp[i-1][0];

}

for(int j=1;j<obstacleGrid[0].length;j++){
if(obstacleGrid[0][j]==1)
dp[0][j]=0;
else
dp[0][j]=dp[0][j-1];
}

for(int i=1;i<obstacleGrid.length;i++){
for(int j=1;j<obstacleGrid[0].length;j++){
if(obstacleGrid[i][j]==1)
dp[i][j]=0;
else {
dp[i][j]=dp[i-1][j]+dp[i][j-1];
}
}
}
return dp[obstacleGrid.length-1][obstacleGrid[0].length-1];
}
}