98 lines
3.3 KiB
C++
98 lines
3.3 KiB
C++
class TrieNode {
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public:
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// initializing one node
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TrieNode(){
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is_word_complete = false;
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// each node can have at most 26 children: a to z.
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for(int i=0;i<26;i++){
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children.push_back(nullptr);
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}
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}
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// so that we can access private member variables.
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friend class Trie;
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private:
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bool is_word_complete;
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std::vector<TrieNode*> children;
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};
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class Trie {
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public:
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// initializing the prefix tree
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Trie() {
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// which basically is initializing the root
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root = new TrieNode;
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}
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void insert(string word) {
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int len = word.length();
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TrieNode* current = root;
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for(int i=0; i<len; i++){
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// inserting a node at the branch of [word[i]-'a'], as the children of current
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// if no one has inserted here yet
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if(current->children[word[i]-'a'] == nullptr){
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// create a node
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TrieNode* node = new TrieNode;
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current->children[word[i]-'a'] = node;
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// after the insertion, update current
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current = current->children[word[i]-'a'];
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}else{
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// else, it means this node is already there, just update current
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// we make the code duplicated here, but this way it's easier to understand.
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current = current->children[word[i]-'a'];
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}
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}
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// when we get out of the for loop, the whole word should have been inserted already, we mark this node as the end of a word.
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current->is_word_complete = true;
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}
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bool search(string word) {
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int len = word.length();
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// once again, starting from root
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TrieNode* current = root;
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for(int i=0; i<len; i++){
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// if this branch we are looking for doesn't exist
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if(current->children[word[i]-'a'] == nullptr){
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return false;
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}else{
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// else update current and keep checking never level
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current = current->children[word[i]-'a'];
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}
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}
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// when we get out of the for loop, the whole word is found, but we still need to make sure this node marks the end of a previously inserted word.
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if(current->is_word_complete == true){
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return true;
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}else{
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// else, it will be like, we are searching for app, but previously we inserted an apple.
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return false;
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}
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}
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bool startsWith(string prefix) {
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int len = prefix.length();
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// once again, starting from root
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TrieNode* current = root;
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for(int i=0; i<len; i++){
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// if this branch we are looking for doesn't exist
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if(current->children[prefix[i]-'a'] == nullptr){
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return false;
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}else{
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// else update current and keep checking never level
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current = current->children[prefix[i]-'a'];
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}
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}
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// since we are only searching for a prefix, when we get here, clearly we found it.
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return true;
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}
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private:
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// just like every tree, we should have a root.
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TrieNode* root;
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};
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/**
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* Your Trie object will be instantiated and called as such:
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* Trie* obj = new Trie();
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* obj->insert(word);
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* bool param_2 = obj->search(word);
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* bool param_3 = obj->startsWith(prefix);
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*/
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