Day14-ImplementTrie.java

class Trie {

    /** Initialize your data structure here. */
    boolean isEnd;
    Trie[] link;
    
    public Trie() {
        isEnd=false;
        link=new Trie[26];
    }
    /** Inserts a word into the trie. */
    public void insert(String word) {
            int i=0;
            char[] ch=word.toCharArray();
            Trie t=this;
            while(t!=null && i<ch.length && t.link[ch[i]-'a']!=null){
                t=t.link[ch[i]-'a'];
                i++;
            }
            if(i==ch.length){ 
                t.isEnd=true;
                return;
            }
        
            for(;i<ch.length;i++){
                Trie temp=new Trie();
                
                t.link[ch[i]-'a']=temp;
                t=temp;
            } 
        
           t.isEnd=true;
        }
        
    
    /** Returns if the word is in the trie. */
    public boolean search(String word) {
        int i=0;
        char[] ch=word.toCharArray();
        Trie t=this;
        while(t!=null && i<ch.length && t.link[ch[i]-'a']!=null){
                t=t.link[ch[i]-'a'];
                i++;
            }
         if(i==ch.length && t.isEnd){
                return true;
            }
        return false;
    }
    
    /** Returns if there is any word in the trie that starts with the given prefix. */
    public boolean startsWith(String prefix) {
         int i=0;
        char[] ch=prefix.toCharArray();
        Trie t=this;
        while(t!=null && i<ch.length && t.link[ch[i]-'a']!=null){
                t=t.link[ch[i]-'a'];
                i++;
            }
         if(i==ch.length){
                return true;
            }
        return false;
    }
}

/**
 * Your Trie object will be instantiated and called as such:
 * Trie obj = new Trie();
 * obj.insert(word);
 * boolean param_2 = obj.search(word);
 * boolean param_3 = obj.startsWith(prefix);
 */