Unique Paths
Question
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?
Answer
这个网格中每一步都可以从上面或者左边走到，所以当前格子的数目等于上面的数值加上左边的数值。
class Solution(object):
def uniquePaths(self, m, n):
"""
:type m: int
:type n: int
:rtype: int
"""
a = [[1 for i in range(n)] for i in range(m)]
for i in range(1, m):
for j in range(1, n):
a[i][j] = a[i-1][j] + a[i][j-1]
return a[m-1][n-1]
