leetcode64. 最小路径和

思路

简单的动态规划，建立dp表，第一行和第一列单独考虑，均为值的累加，
其他格子中的动态方程为： dp[i][j] = grid[i][j] + min(dp[i][j-1],dp[i-1][j])

代码

class Solution:
    def minPathSum(self, grid: List[List[int]]) -> int:
        if not grid: return 0
        m = len(grid[0])
        n = len(grid)
        dp = [[0]*m for i in range(n)]
        dp[0][0] = grid[0][0]
        for i in range(1, n):
            dp[i][0] = dp[i - 1][0] + grid[i][0]
        for j in range(1, m):
            dp[0][j] = dp[0][j - 1] + grid[0][j]

        for i in range(1, n):
            for j in range(1, m):
                dp[i][j] = min(dp[i - 1][j], dp[i][j - 1]) + grid[i][j]
        return dp[-1][-1]