leetcode-208. Implement Trie (Prefix Tree)

leetcode-208. 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.

class TrieNode{
public:
TrieNode *child[26];
bool isWord;
TrieNode():isWord(false){
for(auto &a: child)
a = NULL;
}
};   //Don't forget ;

class Trie {
public:     //Don't forget :
/** 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){     //& is reference, will change the element in the string
int i = a - 'a';
if(!p->child[i])
p->child[i] = new TrieNode;
p = p->child[i];
}
p -> isWord = 1;
}

/** 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;
};

/**
* 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);
*/