Leetcode题解---矩阵的路径

62. 不同路径

 

class Solution:
    def uniquePaths(self, m: int, n: int) -> int:
        dp = [[1]*n] + [[1]+[0] * (n-1) for _ in range(m-1)]
        #print(dp)
        for i in range(1, m):
            for j in range(1, n):
                dp[i][j] = dp[i-1][j] + dp[i][j-1]
        return dp[-1][-1]

64. 最小路径和

 

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