LeetCode-208.Implement Trie (Prefix Tree)

https://leetcode.com/problems/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.

建立Trie树，一种数据结构，需要掌握。

class TrieNode{public:// Initialize your data structure here.TrieNode *children[26];bool isWord;TrieNode(){isWord = false;for (auto &node : children)node = NULL;}};class Trie{public:Trie(){root = new TrieNode();}// Inserts a word into the trie.void insert(string word){TrieNode *node = root;for (char c : word){if (!node->children[c - 'a'])node->children[c - 'a'] = new TrieNode();node = node->children[c - 'a'];}node->isWord = true;}// Returns if the word is in the trie.bool search(string word) {TrieNode *node = root;for (char c : word){if (!node->children[c - 'a'])return false;node = node->children[c - 'a'];}return node->isWord;}// Returns if there is any word in the trie// that starts with the given prefix.bool startsWith(string prefix){TrieNode *node = root;for (char c : prefix){if (!node->children[c - 'a'])return false;node = node->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");

相关链接

hihocoder：http://hihocoder.com/problemset/problem/1014

#include <string>#include <iostream>using namespace std;struct TrieNode{TrieNode *children[26];int count;TrieNode(){count = 1;for (auto &node : children)node = NULL;}};TrieNode* root;void insert(string word){    TrieNode *node = root;    for (char c : word)    {        if (!node->children[c - 'a'])            node->children[c - 'a'] = new TrieNode();        else            node->children[c - 'a']->count++;        node = node->children[c - 'a'];    }}int startsWith(string prefix){    TrieNode *node = root;    for (char c : prefix)    {        if (!node->children[c - 'a'])            return 0;        node = node->children[c - 'a'];    }    return node->count;}int main(){    root = new TrieNode();    int n, m;    string word;    cin >> n;    for (int i = 0; i<n; i++)    {        cin >> word;        insert(word);    }    cin >> m;    for (int i = 0; i<m; i++)    {        cin >> word;        cout << startsWith(word) << endl;    }    return 0;}