63 leetcode - Unique Paths

#!/usr/bin/python
# -*- coding: utf-8 -*-
'''
Unique Paths
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?
'''
class Solution(object):
def uniquePaths(self, m, n):
"""
:type m: int
:type n: int
:rtype: int
"""
if m == 0 or n == 0:
return 0

dp = [[0] * n  for i in range(m)]
for i in range(n):
dp[0][i] = 1
for i in range(m):
dp[i][0] = 1

for row in range(1,m):
for col in range(1,n):
dp[row][col] = dp[row - 1][col] + dp[row][col - 1]

return dp[m-1][n-1]

if __name__ == "__main__":
s = Solution()
print s.uniquePaths(2,2)