class Solution(object):
    def minPathSum(self, grid):
        """
        :type grid: List[List[int]]
        :rtype: int
        """

        m = len(grid)
        n = len(grid[0])

        if m < 2 or n < 2: return sum([sum(i) for i in grid])  # single row or column

        for i in xrange(1, m):             # set first column
            grid[i][0] += grid[i - 1][0]
        for i in xrange(1, n):             # set first row
            grid[0][i] += grid[0][i - 1]

        for i in xrange(1, m):
            for j in xrange(1, n):
                grid[i][j] += grid[i - 1][j] if grid[i - 1][j] < grid[i][j - 1] else grid[i][j - 1]

        return grid[-1][-1]
if __name__ == "__main__":
    answer=Solution()
    print answer.minPathSum([
[1,2],[4,5]
])