leetcode 63. 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]
]
The total number of unique paths is 2.

Note: m and n will be at most 100.

上题：

public int uniquePathsWithObstacles(int[][] obstacleGrid) {        int m = obstacleGrid.length;        if(m == 0) return 0;        int n = obstacleGrid[0].length;        int[][] dp = new int[m][n];        int i,j;        for(int index = m*n-1;index >= 0;index--){            i = index / n;            j = index % n;            if(obstacleGrid[i][j] == 1){                 dp[i][j] = 0;            }            else if(index == m*n-1) dp[i][j] = 1;            else{                dp[i][j] = 0;                if(i+1 < m) dp[i][j] += dp[i+1][j];                if(j+1 < n) dp[i][j] += dp[i][j+1];            }        }        return dp[0][0];    }

加入一个逻辑即可：

if(obstacleGrid[i][j] == 1){                 dp[i][j] = 0;            }