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) { int m = obstacleGrid.length; int n = obstacleGrid[0].length; int[][] dp = new int[m][n]; if (obstacleGrid[0][0] == 1) { return 0; } for(int i = 0;i < m;i++){ for(int j =0; j < n;j++){ if(obstacleGrid[i][j] == 0){ if (i==0 && j==0) dp[i][j] = 1; else dp[i][j] = (i>0? dp[i-1][j] :0) +( j>0? dp[i][j-1]:0); } } } return dp[m-1][n-1]; } }
learned: 这一道题在上一题的基础上，多了障碍物，当我们碰到障碍物的时候，我们无论怎么走也不可能走到这个格子里，所以在这个格子里，累加的路径值为0