LeetCode Unique Paths II

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.

 

和上一题类似，只是有些格不能走。

对于可以走的格,p(i,j)=p(i-1,j)+p(i,j-1);

对于不能走的格,p(i,j)=0;

 

代码：

class Solution {public:int uniquePathsWithObstacles(vector<vector<int> > &obstacleGrid) {int m=obstacleGrid.size();if(m==0)return 0;int n=obstacleGrid[0].size();if(n==0)return 0;vector<vector<int>> paths(m,vector<int>(n,0));int i,j;if(obstacleGrid[0][0]==1)return 0;paths[0][0]=1;for(i=1;i<m;i++)if(obstacleGrid[i][0]==1)paths[i][0]=0;elsepaths[i][0]=paths[i-1][0];for(j=1;j<n;j++)if(obstacleGrid[0][j]==1)paths[0][j]=0;elsepaths[0][j]=paths[0][j-1];for(i=1;i<m;i++)for(j=1;j<n;j++)if(obstacleGrid[i][j]==1)paths[i][j]=0;elsepaths[i][j]=paths[i-1][j]+paths[i][j-1];return paths[m-1][n-1];    }};