Implement a trie with insert, search, and startsWith methods.
Note:
You may assume that all inputs are consist of lowercase letters a-z.
实现字典树，没啥好说的。
class TrieNode {
public:
// Initialize your data structure here.
TrieNode *ch[];
bool isKey;
TrieNode() : isKey(false) {
for (auto &a : ch) a = NULL;
}
};
class Trie {
public:
Trie() {
root = new TrieNode();
}
// Inserts a word into the trie.
void insert(string s) {
TrieNode *p = root;
for (auto &a : s) {
int i = a - 'a';
if (p->ch[i] == NULL) p->ch[i] = new TrieNode();
p = p->ch[i];
}
p->isKey = true;
}
// Returns if the word is in the trie.
bool search(string key) {
TrieNode *p = root;
for (auto &a : key) {
int i = a - 'a';
if (p->ch[i] == NULL) return false;
p = p->ch[i];
}
return p->isKey;
}
// 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->ch[i] == NULL) return false;
p = p->ch[i];
}
return true;
}
private:
TrieNode* root;
};
// Your Trie object will be instantiated and called as such:
// Trie trie;
// trie.insert("somestring");
// trie.search("key");