[leetcode] Implement Trie (Prefix Tree)-优快云博客

本文链接：https://blog.youkuaiyun.com/lmxmimihuhu/article/details/46502957

本文介绍了一种基于C++实现的Trie(字典树)数据结构，并提供了插入、搜索及判断前缀的方法。Trie节点包含是否为单词末尾的标记及26个子节点指针。

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From : https://leetcode.com/problems/implement-trie-prefix-tree/

Implement a trie with insert, search, and startsWith methods.

Note:

You may assume that all inputs are consist of lowercase letters a-z.

Trie中，一个字符串，比如“ab”，它表示为

“ab”是否为一个字典中的串，即’b‘是否是结尾，要看第二行’b‘指向的第三行中的isWord是否为true。

class TrieNode {
public:
    // Initialize your data structure here.
    TrieNode() : isWd(false) {
        for(int i=0; i<26; i++) child[i] = NULL;
    }
    bool isWord() {
        return isWd;
    }
    void setWord() {
        isWd = true;
    }
    TrieNode *getChild(int index) {
        return child[index];
    }
    TrieNode **getChildren() {
        return child;
    }
    void setChild(int index) {
        child[index] = new TrieNode();
    }
private:
    bool isWd;
    TrieNode *child[26];
};

class Trie {
public:
    Trie() {
        root = new TrieNode();
    }

    // Inserts a word into the trie.
    void insert(string s) {
        TrieNode *p = root;
		int size = s.size();
		for(int i=0; i<size; i++) {
			if(!p->getChild(s[i]-'a')) p->setChild(s[i]-'a');
			p = p->getChild(s[i]-'a');
		}
		p->setWord();
    }

    // Returns if the word is in the trie.
    bool search(string key) {
        TrieNode *p = root;
		int size = key.size();
		for(int i=0; i<size; i++) {
			if(!p->getChild(key[i]-'a')) return false;
			p = p->getChild(key[i]-'a');
		}
		return p->isWord();
    }

    // Returns if there is any word in the trie
    // that starts with the given prefix.
    bool startsWith(string prefix) {
        TrieNode *p = root;
		int size = prefix.size();
		for(int i=0; i<size; i++) {
			if(!p->getChild(prefix[i]-'a')) return false;
			p = p->getChild(prefix[i]-'a');
		}
		return true;
    }

private:
    TrieNode* root;
};