unisa_strutture_dati_2013_2014/esercizi/static_methods.java

package esercizi;

import queue.NodeQueue;
import queue.Queue;
import stack.ArrayStack;
import exceptions.*;

/**
 * Created with MONSTER.
 * User: xgiovio
 * Date: 13/04/2014
 * Time: 22:19
 */
public class static_methods {



     // inver a string using a stack
    public static String inverti (String s){
        ArrayStack<Character> a = new ArrayStack<Character>();
        for (int i = 0 ;i< s.length();i++){
            a.push(s.charAt(i));
        }

        String to_return = "";

        for (int i = 0 ;i< s.length();i++){
            to_return += a.pop();
        }

        return to_return;

    }

    // verify is a string of [ and ( is correct  using a stack
    public static boolean checkParentheses (String s) {

        ArrayStack<Character> a = new ArrayStack<Character>();

        for (int i = 0 ; i< s.length();i++){

            if (s.charAt(i)  == '('){
                 a.push(s.charAt(i));
                continue;
            }
            if (s.charAt(i)  == ')'){
                 if (a.isEmpty() ||  a.top() != '('){
                     return false;
                 } else {
                     a.pop();
                 }
                continue;
            }
            if (s.charAt(i)  == '['){
                if (  a.isEmpty() ||  a.top() != '(') {
                    a.push(s.charAt(i));
                } else {
                    return false;
                }
                continue;

            }
            if (s.charAt(i)  == ']'){
                if (a.isEmpty() || a.top() != '['){
                    return false;
                } else {
                    a.pop();
                }
                continue;
            }

        }

        if (a.isEmpty()){
            return true;
        }else {
            return false;
        }

    }

    // verify is a string is palindrome using a stack
    public static boolean isPalindrome (String s){

        ArrayStack<Character> a = new ArrayStack<Character>();

        if (s.length() < 2){
            return true;
        }else {

            boolean pari;

            if (s.length() % 2 == 0) {
                pari = true;
            } else {
                pari = false;
            }


            for (int i= 0 ;i < s.length();i++){
                if (!pari){
                    if (i <= s.length()/2){
                         a.push(s.charAt(i));
                        if (i == s.length()/2 ){
                            a.pop();
                        }
                        continue;
                    }
                } else {
                    if (i <= (s.length()/2) -1){
                        a.push(s.charAt(i));
                        continue;
                    }
                }

                if (s.charAt(i) != a.pop()){
                    return false;
                }

            }
            return true;

        }

    }

    // extract the k element from a Queue Q. k should be >= 0
    public static Integer extract (Queue<Integer> Q, int k) throws NotEnoughElements {

        if (Q.size() <= k) {
            throw new NotEnoughElements();
        } else {
            Integer t = null ;

            for (int i = 0 ;i< Q.size();i++){
                     if (i == k){
                        t = Q.front();
                     }
                     Q.enqueue(Q.dequeue());
            }

           return t;

        }


    }

    // invert a Queue without recursive methods
    public static <E> void reverse (Queue<E> Q){

        NodeQueue<E> newq = new NodeQueue<E>();

        for (;Q.size()> 0;){

            for (int i = 0;i< Q.size() - 1;i++){
                  Q.enqueue(Q.dequeue());
            }
            newq.enqueue(Q.dequeue());
        }

        int size = newq.size();
        for (int i = 0;i<size;i++){
            Q.enqueue(newq.dequeue());
        }
    }

    // invert a Queue with recursion
    public static <E> void recReverse (Queue<E> Q){
        if (Q.size()>1){
            E t = Q.dequeue();
            recReverse(Q);
            Q.enqueue(t);
        }
    }

    // search element x in Queue Q . WARNING THIS FUNCTION ALTER THE ORIGINAL QUEUE Q
    public static <E> boolean isContained (Queue<E>Q,E x){
                if (Q.size() > 0){
                    E t = Q.dequeue();
                    if (t==x){
                        return true;
                    }
                    else{
                        return isContained(Q,x);
                    }
                }else {
                    return false;
                }
    }


}