820. 单词的压缩编码

2021/04/04 leetcode 共 1362 字,约 4 分钟

title

problem link

单词数组 words 的 有效编码 由任意助记字符串 s 和下标数组 indices 组成,且满足:

  • words.length == indices.length
  • 助记字符串 s 以 '#' 字符结尾
  • 对于每个下标 indices[i] ,s 的一个从 indices[i] 开始、到下一个 '#' 字符结束(但不包括 '#')的 子字符串 恰好与 words[i] 相等

给你一个单词数组 words ,返回成功对 words 进行编码的最小助记字符串 s 的长度 。

示例 1:

输入:words = ["time", "me", "bell"]
输出:10
解释:一组有效编码为 s = "time#bell#" 和 indices = [0, 2, 5] 。
words[0] = "time" ,s 开始于 indices[0] = 0 到下一个 '#' 结束的子字符串,如加粗部分所示 "time#bell#"
words[1] = "me" ,s 开始于 indices[1] = 2 到下一个 '#' 结束的子字符串,如加粗部分所示 "time#bell#"
words[2] = "bell" ,s 开始于 indices[2] = 5 到下一个 '#' 结束的子字符串,如加粗部分所示 "time#bell#"

示例 2:

输入:words = ["t"]
输出:2
解释:一组有效编码为 s = "t#" 和 indices = [0] 。

提示:

  • 1 <= words.length <= 2000
  • 1 <= words[i].length <= 7
  • words[i] 仅由小写字母组成

solution

https://github.com/azl397985856/leetcode/blob/master/problems/820.short-encoding-of-words.md

class TrieNode:
    def __init__(self):
        self.count = 0
        self.children = {}


class Solution:
    def minimumLengthEncoding(self, words: List[str]) -> int:
        trie = TrieNode()
        for word in words:
            node = trie
            for c in reversed(word):
                if c not in node.children:
                    node.children[c] = TrieNode()
                node = node.children[c]
            node.count += 1

        def searchIsLeaf(word):
            node = trie
            for c in word:
                if c not in node.children:
                    return False
                node = node.children[c]
            # 这是关键,判断它是否是叶子节点
            return len(node.children) == 0

        # visit = []
        #
        # def dfs(node, cur):
        #     if not node.children:
        #         visit.append(cur)
        #         return
        #     for _, child in node.children.items():
        #         dfs(child, cur + 1)
        #
        # dfs(trie, 0)
        # return len(visit) + sum(visit)

        ans = 0
        for word in words:
            if searchIsLeaf(word[::-1]):
                ans += len(word) + 1
        return ans

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