Implement a Trie -LeetCode-Amazon Interview Question

Find the problem description here.

Trie data structure is an efficient way of performing certain task that hash table is not as optimized for such as auto completion feature, spell checkers e.t.c.

Below, I have implemented Trie data structure that allows to insert a word, search for a word and check if a word starts with a given prefix. Find explanation in the comments !

class TrieNode{
    /*
    TrieNode are nodes that Trie data structure will comprise of
    children is a map that holds the children of a given node
    where key is one of the 26 alphabets and value is a node
    a node can have 26 possible child node
    endOfWord is variable that keeps track at each node
    if that node is the last letter of a word
    */
    public:
    map<char, TrieNode*> children; 
    bool endOfWord; 
};
class Trie {
    private:
    // Tree always starts with a root 
    TrieNode * root;
    
    public:
    Trie() {
        root = new TrieNode();
        
    }
    
    /** Inserts a word into the trie. */
    void insert(string word) {
        
        /*you start with the root to find out where in the tree to
        insert the given word */
        TrieNode * current = root;
        
        for(int i=0; i<word.length(); i++){
      //if the child of the current node is NULL, create a new child
            char ch = word[i];
         if(current->children[ch] == NULL){
             current->children[ch] = new TrieNode();   
         }
            //go to the next node i.e child node 
         current = current->children[ch];
         
        }
           // the last letter will store the information 
          //where it says that it is end of the word
        current->endOfWord = true;
        
    } 
    
    /** Returns if the word is in the trie. */
    bool search(string word) {
          TrieNode * current = root; 
        
          for(int i=0; i<word.length(); i++){
            char ch = word[i];
            /*if the current node does not have child and we are not        
              finished with iterating the word, it means that 
              the word is not present in the trie 
            */
         if(current->children[ch] == NULL){
                return false;
            }
            
            current = current->children[ch];  
        } //end for loop 
        
        /*if at this point no false value has returned then 
        we have the word in the trie, hence return true
        true value comes from the last letter's enOfWord variable
        */
        return current->endOfWord; 
    }
    
    /** Returns if there is any word in the trie that starts with the given prefix. */
    bool startsWith(string prefix) {
        TrieNode * current = root;
        
        int len = prefix.length();
        for(int i=0; i<len; i++){
            
            char ch = prefix[i];
            if(current->children[ch] == NULL){
                return false; 
            }
            
            current = current->children[ch];
        }
        return true;
        
    }
    
};
/**
 * 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);
 */

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