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];    }};