208. Implement Trie (Prefix Tree) LeetCode

题意：实现trie树。
题解：

class TrieNode {
public:
    char var;
    TrieNode* children[26];
    bool isword;
    // Initialize your data structure here.
    TrieNode() {
        var = 0;
        isword = false;
        memset(children,0x0,sizeof(TrieNode*) * 26);
    }
    TrieNode(char c) {
        var = c;
        isword = false;
        memset(children,0x0,sizeof(TrieNode*) * 26);
    }
};

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

    // Inserts a word into the trie.
    void insert(string word) {
        TrieNode* tmp = root;
        int n = word.length();
        for(int i = 0; i < n; i++)
        {
            char c = word[i];
            if(tmp->children[c - 'a'] == 0)
            {
                TrieNode *p = new TrieNode(c);
                tmp->children[c - 'a'] = p;
            }
            tmp = tmp->children[c - 'a'];
        }
        tmp->isword = true;
    }

    // Returns if the word is in the trie.
    bool search(string word) {
        TrieNode* tmp = root;
        int n = word.length();
        for(int i = 0; i < n; i++)
        {
            char c = word[i];
            if(tmp->children[c - 'a'] == 0) return false;
            tmp = tmp->children[c - 'a'];
        }
        if(tmp->isword) return true;
        else return false;
    }

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

private:
    TrieNode* root;
};

// Your Trie object will be instantiated and called as such:
// Trie trie;
// trie.insert("somestring");
// trie.search("key");