leetcode_208 实现Trie(前缀树)

1. 题意

让你实现一个前缀树
实现Trie

2. 题解

需要有一个标记是否到达字符末端的isEnd,和指向子节点的索引数组。

• 代码

class Trie {
public:
    Trie():isEnd(false){
        for ( int i = 0; i < 26;++i)
            child[i] = nullptr;
    }
    ~Trie() {
        for ( int i = 0; i < 26; ++i ) {
            if (child[i]) {
                delete child[i];
                child[i] = nullptr;
            }
        }
    }
    
    void insert(string word) {

        Trie *cur = this;
        int sz = word.size();
        for (int i = 0; i < sz; ++i) {
            int idx = word[i] - 'a';
            if ( cur->child[idx] == nullptr) {
                Trie *nxt = new Trie();
                cur->child[idx] = nxt;
            }

            cur = cur->child[idx];
        }
        cur->isEnd = true;
    }
    
    bool search(string word) {

        Trie *cur = this;

        int sz = word.size();
        for (int i = 0; i < sz; ++i) {
            int idx = word[i] - 'a';
            if (cur->child[idx] == nullptr)
                return false;
            cur = cur->child[idx];
        }
        return cur->isEnd;
    }
    
    bool startsWith(string prefix) {

        int sz = prefix.size();

        Trie *cur = this;
        for (int i = 0; i < sz; ++i ) {
            int idx = prefix[i] - 'a';
            if (cur->child[idx] == nullptr)
                return false;
            cur = cur->child[idx];
        }
        return true;
    }
private:
    bool isEnd;
    Trie *child[26];
};

/**
 * Your Trie object will be instantiated and called as such:
 * Trie* obj = new Trie();
 * obj->insert(word);
 * bool param_2 = obj->search(word);
 * bool param_3 = obj->startsWith(prefix);
 */
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