"""
给定一个包含非负整数的 m x n 网格，请找出一条从左上角到右下角的路径，使得路径上的数字总和为最小。

说明：每次只能向下或者向右移动一步。

示例:

输入:
[
  [1,3,1],
  [1,5,1],
  [4,2,1]
]
输出: 7
解释: 因为路径 1→3→1→1→1 的总和最小。

"""


class Solution:
    def minPathSum(self, grid):
        for i in range(0, len(grid)):
            for j in range(0, len(grid[0])):
                if i == j == 0:
                    grid[i][j] = grid[i][j]
                elif i != 0 and j == 0:
                    grid[i][j] = grid[i - 1][j] + grid[i][j]
                elif i == 0 and j != 0:
                    grid[i][j] = grid[i][j - 1] + grid[i][j]
                else:
                    grid[i][j] = min(grid[i - 1][j], grid[i][j - 1]) + grid[i][j]

        return grid[-1][-1]


s = Solution()
res = s.minPathSum([[1, 3, 1], [1, 5, 1], [4, 2, 1]])
print(res)
