原题地址：https://oj.leetcode.com/problems/unique-paths-ii/

题意：

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.

解题思路：这道题是设置了障碍的，也是用动态规划解决。

代码：

class Solution:    # @param obstacleGrid, a list of lists of integers    # @return an integer    def uniquePathsWithObstacles(self, obstacleGrid):        m = len(obstacleGrid); n = len(obstacleGrid[0])        res = [[0 for i in range(n)] for j in range(m)]        for i in range(m):            if obstacleGrid[i][0] == 0:                res[i][0] = 1            else:                res[i][0] == 0                break        for i in range(n):            if obstacleGrid[0][i] == 0:                res[0][i] = 1            else:                res[0][i] = 0                break        for i in range(1, m):            for j in range(1, n):                if obstacleGrid[i][j] == 1: res[i][j] = 0                else:                    res[i][j] = res[i-1][j] + res[i][j-1]        return res[m-1][n-1]