【题目】
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.
【解析】这道题和上一道题差不多，要从左上角走到右下角，只能向下和向右移动，但是不可以移动到标“1”处的网格中，求一共有多少路径。
这里我还是用的动态规划。
【代码】
public int uniquePathsWithObstacles(int[][] obstacleGrid) { int m=obstacleGrid.length; int n=obstacleGrid[0].length; if(obstacleGrid[m-1][n-1]==1) return 0; else if(m==1&&n==1) return 1; for(int i=m-2;i>=0;i--){ if(obstacleGrid[i][n-1]==1){ obstacleGrid[i][n-1]=0; for(int j=i-1;j>=0;j--) obstacleGrid[j][n-1]=0; break; } else obstacleGrid[i][n-1]=1; } for(int i=n-2;i>=0;i--){ if(obstacleGrid[m-1][i]==1) { obstacleGrid[m-1][i]=0; for(int j=i-1;j>=0;j--) obstacleGrid[m-1][j]=0; break; } else obstacleGrid[m-1][i]=1; } for(int i=m-2;i>=0;i--){ for(int j=n-2;j>=0;j--){ if(obstacleGrid[i][j]==1) obstacleGrid[i][j]=0; else obstacleGrid[i][j]=obstacleGrid[i+1][j]+obstacleGrid[i][j+1]; } } return obstacleGrid[0][0]; }