【python-子集】Generalized Abbreviation（广义缩写）

Write a function to generate the generalized abbreviations of a word.

Example: 
Given word = “word”, return the following list (order does not matter): 
[“word”, “1ord”, “w1rd”, “wo1d”, “wor1”, “2rd”, “w2d”, “wo2”, “1o1d”, “1or1”, “w1r1”, “1o2”, “2r1”, “3d”, “w3”, “4”] 

思路：递归+回溯

class Solution(object):
    def generateAbbreviations(self, word):
        """ :type word: str :rtype: List[str] """

        res = []
        #从0开始遍历，最后0用于计数
        self.helper( 0, word, "", res, 0)
        return res


    def helper(self, index, word, temp_res, res, count):
        #注意这里是len(word)，不是len(word)-1
        if index==len(word):
            if count!=0:
                #组合新的字符串
                temp_res = temp_res[0:-count] + str(count)
            res.append( temp_res )
            return

        # append 1
        self.helper( index+1, word, temp_res+'1', res, count+1)

        # append word
        if count!=0:
            temp_res = temp_res[0:-count] + str(count)
        self.helper( index+1, word, temp_res+word[index], res, 0)  
s=Solution()
print(s.generateAbbreviations("word"))

只能看代码慢慢理解了。

参考：https://www.it610.com/article/5456538.htm