[leetcode]Unique Paths II

新博文地址：[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]
]

The total number of unique paths is 2.

Note: m and n will be at most 100.

 跟Unique Paths几乎木有区别，遇到obstacleGrid[i][j] == 1的元素，即将path设为0即可。需要注意的是，在第一行和第一列，即obstacleGrid[i][0] == 1&& obstacleGrid[0][i] == 1后面的元素path全部置0

    public int uniquePathsWithObstacles(int[][] obstacleGrid) {
    	if(obstacleGrid == null || obstacleGrid.length == 0){
    		return 0;
    	}
    	int m = obstacleGrid.length;
    	int n = obstacleGrid[0].length;
    	int[][] path = new int[m][n];
    	for(int i = 0; i < n; i++){
    		if(obstacleGrid[0][i] == 0){
    			path[0][i] = 1;
    		}else{
    			path[0][i] = 0;
    			break;
    		}
    	}
    	for(int i = 0; i < m; i++){
    		if(obstacleGrid[i][0] == 0){
    			path[i][0] = 1;
    		}else{
    			path[i][0] = 0;
    			break;
    		}
    	}
    	for (int i = 1; i < m; i++) {
			for (int j = 1; j < n; j++) {
				if(obstacleGrid[i][j] == 0){
					path[i][j] = path[i-1][j] + path[i][j-1];
				}
			}
		}
		return path[m-1][n-1];
    }