Leetcode ---- Trie topic

Leetcode ---- Trie topic

I. Implement Trie (Prefix Tree)

Question:

 

Implement a trieinsert,search, AndstartsWithMethods.

Note:
You may assume that all inputs are consist of lowercase lettersa-z.

Analysis: this is a typical trie tree, see http://blog.csdn.net/lu597203933/article/details/44227431

Code:

 

class TrieNode {public:    // Initialize your data structure here.    TrieNode() {        for(int i = 0; i < 26; i++)            next[i] = NULL;        isString = false;    }    TrieNode *next[26];    bool isString;};class Trie {public:    Trie() {        root = new TrieNode();            }    // Inserts a word into the trie.    void insert(string s) {        TrieNode *p = root;        for(int i = 0; i < s.size(); i++){            if(p->next[s[i]-'a'] == NULL){                p->next[s[i]-'a'] = new TrieNode();            }            p = p->next[s[i]-'a'];        }        p->isString = true;    }    // Returns if the word is in the trie.    bool search(string key) {        TrieNode *p = root;        for(int i = 0; i < key.size(); i++){            if(p == NULL) return false;            p = p->next[key[i]-'a'];        }        if(p == NULL || p->isString == false) return false;        return true;            }    // Returns if there is any word in the trie    // that starts with the given prefix.    bool startsWith(string prefix) {        TrieNode *p = root;        for(int i = 0; i <= prefix.size(); i++){            if(p == NULL) return false;            p = p->next[prefix[i]-'a'];        }        return true;    }private:    TrieNode* root;};// Your Trie object will be instantiated and called as such:// Trie trie;// trie.insert("somestring");// trie.search("key");