README.md

648. 单词替换

English Version

题目描述

在英语中，我们有一个叫做 词根(root)的概念，它可以跟着其他一些词组成另一个较长的单词——我们称这个词为 继承词(successor)。例如，词根an，跟随着单词 other(其他)，可以形成新的单词 another(另一个)。

现在，给定一个由许多词根组成的词典和一个句子。你需要将句子中的所有继承词用词根替换掉。如果继承词有许多可以形成它的词根，则用最短的词根替换它。

你需要输出替换之后的句子。

 

示例 1：

输入：dictionary = ["cat","bat","rat"], sentence = "the cattle was rattled by the battery"
输出："the cat was rat by the bat"

示例 2：

输入：dictionary = ["a","b","c"], sentence = "aadsfasf absbs bbab cadsfafs"
输出："a a b c"

示例 3：

输入：dictionary = ["a", "aa", "aaa", "aaaa"], sentence = "a aa a aaaa aaa aaa aaa aaaaaa bbb baba ababa"
输出："a a a a a a a a bbb baba a"

示例 4：

输入：dictionary = ["catt","cat","bat","rat"], sentence = "the cattle was rattled by the battery"
输出："the cat was rat by the bat"

示例 5：

输入：dictionary = ["ac","ab"], sentence = "it is abnormal that this solution is accepted"
输出："it is ab that this solution is ac"

 

提示：

• 1 <= dictionary.length <= 1000
• 1 <= dictionary[i].length <= 100
• dictionary[i] 仅由小写字母组成。
• 1 <= sentence.length <= 10^6
• sentence 仅由小写字母和空格组成。
• sentence 中单词的总量在范围 [1, 1000] 内。
• sentence 中每个单词的长度在范围 [1, 1000] 内。
• sentence 中单词之间由一个空格隔开。
• sentence 没有前导或尾随空格。

解法

前缀树实现。

Python3

class Trie:
    def __init__(self) -> None:
        self.children = [None] * 26
        self.root = None


class Solution:
    def replaceWords(self, dictionary: List[str], sentence: str) -> str:
        trie = Trie()
        for root in dictionary:
            cur = trie
            for c in root:
                idx = ord(c) - ord('a')
                if cur.children[idx] is None:
                    cur.children[idx] = Trie()
                cur = cur.children[idx]
            cur.root = root

        ans = []
        for word in sentence.split():
            cur = trie
            for c in word:
                idx = ord(c) - ord('a')
                if cur.children[idx] is None or cur.root is not None:
                    break
                cur = cur.children[idx]
            ans.append(word if cur.root is None else cur.root)
        return ' '.join(ans)

Java

class Trie {
    Trie[] children = new Trie[26];
    String root;
}

class Solution {
    public String replaceWords(List<String> dictionary, String sentence) {
        Trie trie = new Trie();
        for (String root : dictionary) {
            Trie cur = trie;
            for (char c : root.toCharArray()) {
                if (cur.children[c - 'a'] == null) {
                    cur.children[c - 'a'] = new Trie();
                }
                cur = cur.children[c - 'a'];
            }
            cur.root = root;
        }
        List<String> ans = new ArrayList<>();
        for (String word : sentence.split("\\s+")) {
            Trie cur = trie;
            for (char c : word.toCharArray()) {
                if (cur.children[c - 'a'] == null || cur.root != null) {
                    break;
                }
                cur = cur.children[c - 'a'];
            }
            ans.add(cur.root == null ? word : cur.root);
        }
        return String.join(" ", ans);
    }
}

C++

class Trie {
public:
    string root;
    vector<Trie*> children;

    Trie() {
        root = "";
        children.resize(26);
    }
};

class Solution {
public:
    string replaceWords(vector<string>& dictionary, string sentence) {
        Trie* trie = new Trie();
        for (auto root : dictionary)
        {
            Trie* cur = trie;
            for (char c : root)
            {
                if (!cur->children[c - 'a']) cur->children[c - 'a'] = new Trie();
                cur = cur->children[c - 'a'];
            }
            cur->root = root;
        }

        string ans = "";
        istringstream is(sentence);
        vector<string> ss;
        string s;
        while (is >> s) ss.push_back(s);
        for (auto word : ss)
        {
            Trie* cur = trie;
            for (char c : word)
            {
                if (!cur->children[c - 'a'] || cur->root != "") break;
                cur = cur->children[c - 'a'];
            }
            ans += cur->root == "" ? word : cur->root;
            ans += " ";
        }
        ans.pop_back();
        return ans;
    }
};

Go

func replaceWords(dictionary []string, sentence string) string {
	trie := &Trie{}
	for _, root := range dictionary {
		cur := trie
		for _, c := range root {
			c -= 'a'
			if cur.children[c] == nil {
				cur.children[c] = &Trie{}
			}
			cur = cur.children[c]
		}
		cur.root = root
	}

	var ans []string
	for _, word := range strings.Split(sentence, " ") {
		cur := trie
		for _, c := range word {
			c -= 'a'
			if cur.children[c] == nil || cur.root != "" {
				break
			}
			cur = cur.children[c]
		}
		if cur.root == "" {
			ans = append(ans, word)
		} else {
			ans = append(ans, cur.root)
		}
	}
	return strings.Join(ans, " ")
}

type Trie struct {
	children [26]*Trie
	root     string
}

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