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