Leetcode: Edit Distance

Question

Given two words word1 and word2, find the minimum number of steps required to convert word1 to word2. (each operation is counted as 1 step.)

You have the following 3 operations permitted on a word:

a) Insert a character

b) Delete a character

c) Replace a character

Hide Tags Dynamic Programming String

Hide Similar Problems (M) One Edit Distance

Solution

[code]class Solution(object):
    def minDistance(self, word1, word2):
        """
        :type word1: str
        :type word2: str
        :rtype: int
        """

        l1, l2 = len(word1), len(word2)

        # res[i][j] means res for the first i elems in word1, and the first j elems in word2
        dp, backup = range(l1+1), [0]*(l1+1)

        for s2ind in range(1,l2+1):
            backup[0] = s2ind
            for s1ind in range(1,l1+1):
                if word1[s1ind-1]==word2[s2ind-1]:
                    backup[s1ind] = dp[s1ind-1]
                else:
                    backup[s1ind] = min( backup[s1ind-1], dp[s1ind-1], dp[s1ind]) + 1

            dp = backup[:]

        return dp[-1]