_145unique.java

public class _145unique {
    static class Node{
        Node[] children = new Node[26];
        boolean eow;
        public Node(){
            for(int i=0;i<children.length;i++){
                children[i]=null;
            }
        }
    }
    public static Node root = new Node();
    public static void insert(String word){
        int level = 0;
        int len = word.length();
        int idx = 0;

        Node curr = root;
        for(;level<len;level++){
            idx=word.charAt(level)-'a';
            if(curr.children[idx]==null){
                curr.children[idx] = new Node();
            }
            curr=curr.children[idx];
        }
        curr.eow=true;
    }
    public static boolean search(String key){
        int level = 0;
        int len = key.length();
        int idx = 0;

        Node curr = root;
        for(;level<len;level++){
            idx=key.charAt(level)-'a';
            if(curr.children[idx]==null){
                return false;
            }
            curr=curr.children[idx];
        }
        return curr.eow==true;
    }
    public static int countNodes(Node root){
        if(root==null){
            return 0;
        }
        int count = 0;
        for(int i=0;i<26;i++){
            if(root.children[i]!=null){
                count += countNodes(root.children[i]);
            }
        }
        return count+1;
    }
    public static void main(String[] args) {
        String str = "ababa";
        for(int i = 0;i<str.length();i++){
            String suffix = str.substring(i);
            insert(suffix);
        }
        System.out.println(countNodes(root));
    }
}