63. 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.

思路

本题和上一篇博客Unique Paths很类似，唯一区别就是，当遇到当前位置为1，需要将res[j]清0.

代码

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

}
}
return res[n-1];
}
};