#Leet Code# Unique Path

 1 class Solution:
 2     # @return an integer
 3     def __init__(self):
 4         self.record = {}
 5 
 6     def uniquePaths(self, m, n):
 7         if m == 0 or n == 0: return 0 
 8         if m == 1 or n == 1: return 1
 9 
10         if (m-1, n) in self.record:
11             a = self.record[(m-1, n)]
12         else:
13             a = self.uniquePaths(m-1, n) 
14             self.record[(m-1, n)] = a
15 
16         if (m, n-1) in self.record:
17             b = self.record[(m, n-1)]
18         else:
19             b = self.uniquePaths(m, n-1)
20             self.record[(m, n-1)] = b
21 
22         return a + b 
23 
24 foo = Solution()
25 print foo.uniquePaths(1, 2)