Tries.java

Tries.java

public class Tries {


    public static void main(String[] args) {
        Node n = new Node();
        n.add("ciao");
        n.add("ciaone");
        n.printWords();
        System.out.println();
        n.delete("ciaone");
        System.out.println();
        n.printWords();
    }


    public static class Node {
        Map<Character, Node> children = new HashMap<>();
        boolean stopWord = false;

        public void add(String input) {
            add(input, 0);
        }

        private void add(String input, int index) {
            Character c = input.charAt(index);
            Node child;
            if (children.containsKey(c)) {
                child = children.get(c);
            } else {
                child = new Node();
                children.put(c, child);
            }
            if (index == input.length() - 1) {
                stopWord = true;
                return;
            }
            child.add(input, index + 1);
        }

        public boolean search(String search) {
            return search(search, 0);
        }

        private boolean search(String search, int index) {
            if (index == search.length()) {
                return false;
            }
            if (children.containsKey(search.charAt(index))) {
                if (index == search.length() - 1 && stopWord) {
                    return true;
                }
                return children.get(search.charAt(index)).search(search, index + 1);
            } else {
                return false;
            }
        }

        public void delete(String delete) {
            if (search(delete)) {
                delete(delete, 0);
            }
        }

        private boolean delete(String delete, int i) {
            if (delete.length() - 1 == i) {
                if (!stopWord) {
                    return false;
                }
                children.remove(delete.charAt(i));
                return children.size() == 0;
            }
            char ch = delete.charAt(i);
            Node child = children.get(ch);
            if (child == null) {
                return false;
            }
            boolean shouldDelete = child.delete(delete, i + 1);
            if (shouldDelete && !stopWord) {
                children.remove(ch);
                return children.size() == 0;
            }
            return false;
        }

        public void printWords() {
            List<String> words = new LinkedList<>();
            print(new StringBuilder(), words);
            for (String s : words) {
                System.out.println(s);
            }
        }

        public void print(StringBuilder sb, List<String> words) {
            for (Character c : children.keySet()) {
                sb.append(c);
                if (stopWord) {
                    words.add(sb.toString());
                }
                Node child = children.get(c);
                child.print(sb, words);
            }
        }
    }
}