给定两个单词 word1 和 word2，计算出将 word1 转换成 word2 所使用的最少操作数 。

你可以对一个单词进行如下三种操作：

插入一个字符

删除一个字符

替换一个字符

示例 1:

输入: word1 = "horse", word2 = "ros"

输出: 3

解释:

horse -> rorse (将 'h' 替换为 'r')

rorse -> rose (删除 'r')

rose -> ros (删除 'e')

示例 2:

输入: word1 = "intention", word2 = "execution"

输出: 5

解释:

intention -> inention (删除 't')

inention -> enention (将 'i' 替换为 'e')

enention -> exention (将 'n' 替换为 'x')

exention -> exection (将 'n' 替换为 'c')

exection -> execution (插入 'u')

 

 

 

 

 

1 class Solution: 2     def minDistance(self, string1: str, string2: str) -> int: 3         m = len(string1) 4         n = len(string2) 5         f = [[None for _ in range(n+1)] for i in range(m+1)] 6         for i in range (m+1): 7             for j in range(n+1): 8                 if i== 0: 9                     f[i][j]=j10                     continue11                 if j == 0:12                     f[i][j] = i13                     continue14                     #insert delete replace15                 if string1[i-1] == string2[j-1]:16                     f[i][j]=f[i-1][j-1]17                 else:18                     f[i][j] = min(f[i-1][j],f[i][j-1],f[i-1][j-1]) + 119         return f[-1][-1]

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