【leetcode】Unique Paths II

Unique Paths II

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.



The total number of unique paths is 2.

思路：

还是用动态规划做，主要是当数值为1的时候，就没法走了，则之前记录的值得清空。

class Solution {
public:
int uniquePathsWithObstacles(vector<vector<int>>& obstacleGrid) {
int n=obstacleGrid.size();
if(n==0) return 0;
int m=obstacleGrid[0].size();
if(obstacleGrid[0][0]==1) return 0;

vector<int> f(m,0);
f[0]=1;

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