Implement a trie with insert, search, and startsWith methods.
Have you met this question in a real interview?
Example
Note
You may assume that all inputs are consist of lowercase letters a-z.
LeetCode上的原题，请参见我之前的博客Implement Trie (Prefix Tree) 实现字典树(前缀树)。
/**
* Your Trie object will be instantiated and called as such:
* Trie trie;
* trie.insert("lintcode");
* trie.search("lint"); will return false
* trie.startsWith("lint"); will return true
*/
class TrieNode {
public:
// Initialize your data structure here.
TrieNode *child[26];
bool isWord;
TrieNode(): isWord(false) {
for (auto & a : child) a = NULL;
}
};
class Trie {
public:
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:
TrieNode* root;
};
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