【leetcode】712. Minimum ASCII Delete Sum for Two Strings

题目如下：

解题思路：本题和【leetcode】583. Delete Operation for Two Strings 类似，区别在于word1[i] != word2[j]的时候，是删除word1[i]还是word2[j]取决于min(dp[i-1][j]+ord(word1[i-1]),dp[i][j-1]+ord(word2[j-1]))。

代码如下：

class Solution(object):
    def minimumDeleteSum(self, s1, s2):
        """
        :type s1: str
        :type s2: str
        :rtype: int
        """
        word1 = s1
        word2 = s2
        if len(word1) == 0 or len(word2) == 0:
            return abs(len(word2) - len(word1))
        dp = [[0 for x in range(len(word2)+1)] for x in range(len(word1)+1)]
        w1_ascii = 0
        w2_ascii = 0
        for i in xrange(1,len(word1)+1):
            w1_ascii += ord(word1[i-1])
            dp[i][0] = w1_ascii
        for j in xrange(1,len(word2)+1):
            w2_ascii += ord(word2[j-1])
            dp[0][j] = w2_ascii
        for i in xrange(1,len(word1)+1):
            for j in xrange(1,len(word2)+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]+ord(word1[i-1]),dp[i][j-1]+ord(word2[j-1]))
        return dp[-1][-1]