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题目来源
https://leetcode.com/problems/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.
题意分析
Input:a matrix as list[list[int]]
Output:the number of path
Conditions:从左上角走到左下角，注意有障碍不能通过
题目思路
上一题是用数学方法直接解，这一题用动态规划吧，因为每一步都会基于上一格或者是左一格，动态方程为dp[i][j] = dp[i][j-1] + dp[i-1][j]
注意初始化的时候如果遇到障碍，后面的位置不能初始化为0了
AC代码（Python）
1 class Solution(object): 2 def uniquePathsWithObstacles(self, obstacleGrid): 3 """ 4 :type obstacleGrid: List[List[int]] 5 :rtype: int 6 """ 7 m = len(obstacleGrid) 8 n = len(obstacleGrid[0]) 9 dp = [[0 for i in range(n)] for j in range(m)] 10 for i in range(n): 11 if obstacleGrid[0][i] == 1: 12 break 13 else: 14 dp[0][i] = 1 15 16 for i in range(m): 17 if obstacleGrid[i][0] == 1: 18 break 19 else: 20 dp[i][0] = 1 21 22 for i in range(1, m): 23 for j in range(1, n): 24 if obstacleGrid[i][j] == 0: 25 dp[i][j] = dp[i - 1][j] + dp[i][j - 1] 26 27 return dp[m - 1][n - 1]
[LeetCode]题解（python）：063-Unique path II
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原文地址：http://www.cnblogs.com/loadofleaf/p/5093528.html
