原题地址：https://oj.leetcode.com/problems/unique-paths/
题意：
A robot is located at the top-left corner of a m x n grid (marked ‘Start‘ in the diagram below).
The robot can only move either down or right at any point in time. The robot is trying to reach the bottom-right corner of the grid (marked ‘Finish‘ in the diagram below).
How many possible unique paths are there?
Above is a 3 x 7 grid. How many possible unique paths are there?
Note: m and n will be at most 100.
解题思路：这道题和climbing stairs很像，可以用动态规划解决。状态转移方程为dp[i][j]=dp[i-1][j]+dp[i][j-1]。
代码：
class Solution: # @return an integer def uniquePaths(self, m, n): if m == 1 and n == 1: list = [[1]] elif m == 1 and n > 1: list = [[1 for i in range(n)]] elif m > 1 and n == 1: list = [[1] for i in range(m)] else: list = [[0 for i in range(n)] for i in range(m)] for i in range(0, n): list[0][i] = 1 for i in range(0, m): list[i][0] = 1 for i in range(1, m): for j in range(1, n): list[i][j] = list[i-1][j] + list[i][j-1] return list[m-1][n-1]