代码：
class Solution: def minDistance(self, word1: str, word2: str) -> int: l1 = len(word1) l2 = len(word2) dp = [[0 for _ in range(l2+1)] for _ in range(l1+1)] for i in range(l1+1): dp[i][0] = i for j in range(l2+1): dp[0][j] = j for i in range(1, l1+1): for j in range(1, l2+1): if word1[i-1] == word2[j-1]:dp[i][j] = dp[i-1][j-1] else:dp[i][j] = min(dp[i-1][j], dp[i][j-1], dp[i-1][j-1]) + 1 return dp[l1][l2]
