[Leetcode prefix tree (dictionary tree, Trie) C++] 208. Implement Trie (Prefix Tree)

208. Implement Trie (Prefix Tree)

class TrieNode {
    
    
public:
    bool is_end;
    vector<TrieNode*> children = vector<TrieNode*>(26, nullptr); //明确这是一个成员变量声明;
    TrieNode() {
    
     is_end = false;}
};


class Trie {
    
    
public:
    TrieNode* root = new TrieNode();
    TrieNode* p;
    /** Initialize your data structure here. */
    Trie() {
    
    
    }
    
    /** Inserts a word into the trie. */
    void insert(string word) {
    
    
        int len = word.size();
        p = root;
        for(int ii = 0; ii < len; ii++) {
    
    
            if(!p->children[word[ii] - 'a']) p->children[word[ii] - 'a'] = new TrieNode();
            p = p->children[word[ii] - 'a'];
        }
        p->is_end = true;
    }
    
    /** Returns if the word is in the trie. */
    bool search(string word) {
    
    
        int len = word.size();
        p = root;
        for(int ii = 0; ii < len; ii++) {
    
    
            if(!p->children[word[ii] - 'a']) return false;
            p = p->children[word[ii] - 'a'];
        }
        return p->is_end;
    }
    
    /** Returns if there is any word in the trie that starts with the given prefix. */
    bool startsWith(string prefix) {
    
    
        int len = prefix.size();
        p = root;
        for(int ii = 0; ii < len; ii++) {
    
    
            if(!p->children[prefix[ii] - 'a']) return false;
            p = p->children[prefix[ii] - 'a'];
        }
        return true;
    }
};

/**
 * 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);
 */