MostFrequentSubstring.java

package zad3;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Collections;

class MapEntry<K extends Comparable<K>,E> implements Comparable<K> {

    K key;
    E value;

    public MapEntry (K key, E val) {
        this.key = key;
        this.value = val;
    }

    public int compareTo (K that) {
        @SuppressWarnings("unchecked")
        MapEntry<K,E> other = (MapEntry<K,E>) that;
        return this.key.compareTo(other.key);
    }

    public String toString () {
        return "(" + key + "," + value + ")";
    }
}

class SLLNode<E> {
    protected E element;
    protected SLLNode<E> succ;

    public SLLNode(E elem, SLLNode<E> succ) {
        this.element = elem;
        this.succ = succ;
    }

    @Override
    public String toString() {
        return element.toString();
    }
}

class CBHT<K extends Comparable<K>, E> {

    private SLLNode<MapEntry<K,E>>[] buckets;

    @SuppressWarnings("unchecked")
    public CBHT(int m) {
        buckets = (SLLNode<MapEntry<K,E>>[]) new SLLNode[m];
    }

    private int hash(K key) {
        return Math.abs(key.hashCode()) % buckets.length;
    }

    public SLLNode<MapEntry<K,E>> search(K targetKey) {
        int b = hash(targetKey);
        for (SLLNode<MapEntry<K,E>> curr = buckets[b]; curr != null; curr = curr.succ) {
            if (targetKey.equals(((MapEntry<K, E>) curr.element).key))
                return curr;
        }
        return null;
    }

    public void insert(K key, E val) {      // Insert the entry <key, val> into this CBHT.
        MapEntry<K, E> newEntry = new MapEntry<K, E>(key, val);
        int b = hash(key);
        for (SLLNode<MapEntry<K,E>> curr = buckets[b]; curr != null; curr = curr.succ) {
            if (key.equals(((MapEntry<K, E>) curr.element).key)) {
                curr.element = newEntry;
                return;
            }
        }
        buckets[b] = new SLLNode<MapEntry<K,E>>(newEntry, buckets[b]);
    }

    public void delete(K key) {
        int b = hash(key);
        for (SLLNode<MapEntry<K,E>> pred = null, curr = buckets[b]; curr != null; pred = curr, curr = curr.succ) {
            if (key.equals(((MapEntry<K,E>) curr.element).key)) {
                if (pred == null)
                    buckets[b] = curr.succ;
                else
                    pred.succ = curr.succ;
                return;
            }
        }
    }

    public String toString() {
        String temp = "";
        for (int i = 0; i < buckets.length; i++) {
            temp += i + ":";
            for (SLLNode<MapEntry<K,E>> curr = buckets[i]; curr != null; curr = curr.succ) {
                temp += curr.element.toString() + " ";
            }
            temp += "\n";
        }
        return temp;
    }

}

public class MostFrequentSubstring {
    public static void main (String[] args) throws IOException {
        CBHT<String,Integer> tabela = new CBHT<String,Integer>(300);
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

        String word = br.readLine().trim();
        ArrayList<String> all = new ArrayList<String>();

        for (int i=0; i<word.length(); i++) {
            String tmp = "";
            for (int j=i; j<word.length(); j++) {
                tmp += word.charAt(j);
                all.add(tmp);
            }
        }

        for (String w : all) {
            SLLNode<MapEntry<String, Integer>> c = tabela.search(w);
            if (c == null) {
                tabela.insert(w, 1);
            } else {
                int count = c.element.value;
                tabela.insert(w, count+1);
            }
        }

        int max = 1;
        ArrayList<String> najg = new ArrayList<String>();

        for (String w : all) {
            SLLNode<MapEntry<String, Integer>> c = tabela.search(w);
            if (c != null) {
                int count = c.element.value;

                if (count > max) {
                    max = count;
                    najg = new ArrayList<String>();
                    najg.add(c.element.key);
                } else if (count == max) {
                    najg.add(c.element.key);
                }
            }
        }

        if (najg.size() == 1) {
            System.out.println(najg.get(0));
            return;
        }

        ArrayList<String> najdolgi = new ArrayList<String>();
        max = 0;

        for (String w : najg) {
            if (w.length() > max) {
                max = w.length();
                najdolgi = new ArrayList<String>();
                najdolgi.add(w);
            } else if (w.length() == max) {
                najdolgi.add(w);
            }
        }

        if (najdolgi.size() == 1) {
            System.out.println(najdolgi.get(0));
            return;
        }

        Collections.sort(najdolgi);

        System.out.println(najdolgi.get(0));

    }
}