[LeetCode] Implement Trie (Prefix Tree)

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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.

解题思路：

前缀树。由于值设定为在a-z之间，我们可以假设是一棵26叉树。注意，每个节点还需要加入一个标记，表明从根到这个节点的路径组成的序列是否为单词。

class TrieNode {public:    // Initialize your data structure here.    TrieNode() {        this->bWord=false;        for(int i=0; i<26; i++){            this->son[i] = NULL;        }    }        TrieNode* getSon(char c){        return this->son[c-'a'];    }        void setSon(int i, TrieNode* node){        this->son[i] = node;    }        bool isWord(){        return this->bWord;    }        void markAsWord(){        this->bWord = true;    }private:    bool bWord;    TrieNode* son[26];};class Trie {public:    Trie() {        root = new TrieNode();    }    // Inserts a word into the trie.    void insert(string s) {        int len = s.length();        TrieNode* parent = root, *node;        for(int i=0;i<len; i++){            node = parent->getSon(s[i]);            if(node == NULL){                node=new TrieNode();                parent->setSon(s[i] - 'a', node);            }            parent = node;        }        parent->markAsWord();    }    // Returns if the word is in the trie.    bool search(string key) {        int len = key.length();        TrieNode* node = root;        for(int i=0; i<len; i++){            node = node->getSon(key[i]);            if(node==NULL){                return false;            }        }        return node->isWord();    }    // Returns if there is any word in the trie    // that starts with the given prefix.    bool startsWith(string prefix) {        int len = prefix.length();        TrieNode* node = root;        for(int i=0; i<len; i++){            node = node->getSon(prefix[i]);            if(node==NULL){                return false;            }        }        return true;    }private:    TrieNode* root;};// Your Trie object will be instantiated and called as such:// Trie trie;// trie.insert("somestring");// trie.search("key");

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