Implementing Tries

Abhinay Gupta

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Jul 11, 2021

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class Trie {
    class TrieNode{
        Map<Character,TrieNode> children = new HashMap<>();
        boolean isLeaf;
    }
    private TrieNode root;
    /** Initialize your data structure here. */
    public Trie() {
        root= new TrieNode();
    }    
    /** Inserts a word into the trie. */
    public void insert(String word) {
        TrieNode node = root;
        for(char c : word.toCharArray()){
            if(!node.children.containsKey(c)){
                
                node.children.put(c,new TrieNode());
            }
            node = node.children.get(c);
        }
        node.isLeaf= true;
    } 
    /** Returns if the word is in the trie. */
    public boolean search(String word) {
        TrieNode p = root;
        for(char c : word.toCharArray()) {
            if(!p.children.containsKey(c)) {
                return false;
            }
            p = p.children.get(c);
        }
        return p.isLeaf;
    }
    
    /** Returns if there is any word in the trie that starts with the given prefix. */
    public boolean startsWith(String prefix) {
        TrieNode p = root;
        for(char c : prefix.toCharArray()) {
            if(!p.children.containsKey(c)) {
                return false;
            }
            p = p.children.get(c);
        }
        return true;
    }
}