[leetcode]Unique Paths II

Unique Paths II

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]
]

算法思路：

跟[leetcode]Unique Paths几乎一样，就加上一个判断好了。

代码如下：

public class Solution {
    public int uniquePathsWithObstacles(int[][] obstacleGrid) {
        if(obstacleGrid == null || obstacleGrid.length == 0) return 0;
        int height = obstacleGrid.length;
        int width = obstacleGrid[0].length;
        int[][] dp = new int[height][width];
        for(int i = 0; i < width;i++){
            if(obstacleGrid[0][i] == 0){
                dp[0][i] = 1;
            }else{
                break;
            }
        }
        for(int i = 0; i < height;i++){
            if(obstacleGrid[i][0] == 0){
                dp[i][0] = 1;
            }else{
                break;
            }
        }
        for(int i = 1; i < height; i++){
            for(int j = 1; j < width;j++){
                if(obstacleGrid[i][j] == 0)
                    dp[i][j] = dp[i - 1][j] + dp[i][j - 1];
            }
        }
        return dp[height - 1][width - 1];    
    }
}