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;
else
paths[i][0]=paths[i-1][0];
for(j=1;j<n;j++)
if(obstacleGrid[0][j]==1)
paths[0][j]=0;
else
paths[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;
else
paths[i][j]=paths[i-1][j]+paths[i][j-1];
return paths[m-1][n-1];
}
};