68 leetcode - Minimum Path Sum

#!/usr/bin/python# -*- coding: utf-8 -*-'''Minimum Path SumGiven a m x n grid filled with non-negative numbers, find a path from top left to bottom right which minimizes the sum of all numbers along its path.Note: You can only move either down or right at any point in time.'''class Solution(object):    def minPathSum(self, grid):        """        :type grid: List[List[int]]        :rtype: int        """        m = len(grid)        if 0 == m:            return 0        n = len(grid[0])        if 0 == n:            return 0        dp = [[0] * n for i in  range(m)]  #a = [[0] * n] * m,不能使用这个,因为引用,id(a[m])相同        dp[0][0] = grid[0][0]        for i in range(1,m):            dp[i][0] = dp[i - 1][0] + grid [i][0]        for i in range(1,n):            dp[0][i] = dp[0][i - 1] + grid[0][i]        for row in range(1,m):            for col in range(1,n):                dp[row][col] = grid[row][col] + min(dp[row - 1][col], dp[row][col - 1])        return dp[m - 1][n - 1]if __name__ == "__main__":    s = Solution()    print s.minPathSum([[1,3,1],[1,5,1],[4,2,1]])