题目难度★★★
题目描述
实现一个 Trie (前缀树),包含 insert, search, 和 startsWith 这三个操作。
示例:
Trie trie = new Trie();
trie.insert("apple");
trie.search("apple"); // 返回 true
trie.search("app"); // 返回 false
trie.startsWith("app"); // 返回 true
trie.insert("app");
trie.search("app"); // 返回 true
题目地址 https://leetcode-cn.com/problems/implement-trie-prefix-tree
实现代码
class Trie {
public:
/** Initialize your data structure here. */
Trie(){
root = new TrieNode();
}
/** Inserts a word into the trie. */
void insert(string word) {
TrieNode* p = root;
for (auto& a : word) {
int i = a - 'a';
if (!p->child[i])
p->child[i] = new TrieNode();
p = p->child[i];
}
p->isWord = true;
}
/** Returns if the word is in the trie. */
bool search(string word) {
TrieNode* p = root;
for (auto& a : word) {
int i = a - 'a';
if (!p->child[i])
return false;
p = p->child[i];
}
return p->isWord;
}
/** Returns if there is any word in the trie that starts with the given prefix. */
bool startsWith(string prefix) {
TrieNode* p = root;
for (auto& a : prefix) {
int i = a - 'a';
if (!p->child[i])
return false;
p = p->child[i];
}
return true;
}
private:
struct TrieNode
{
TrieNode():isWord(false){
for (auto &a:child)
{
a = NULL;
}
}
TrieNode* child[26];
bool isWord;
};
TrieNode* root;
};
/** * 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); */