2

ユーザー入力を先入れ先出しで出力するプログラムを作成しようとしています。現在、スタック LIFO (後入れ先出し) を出力するプログラムを作成しました。ただし、スタックの出力を FIFO (先入れ先出し) 順で表示するキューを実装するにはどうすればよいでしょうか。

以下の私のコード：

import java.util.*;

public class stackReversal {

    private class Node {
        private String item;
        private Node next;
    }

    private Node first = null;

    public boolean isEmpty() {
        return (first == null);
    }

    public void push(String s) {
        Node node = new Node();
        node.item = s;
        node.next = first;

        first = node;
    }

    public String pop() {
        if (first == null)
            throw new RuntimeException("Stack Empty!");
        String result = first.item;
        first = first.next;
        return result;

    }

    public String popString() {
        String result = "";
        Node current = first;

        while (current != null) {
            result += current.item;
            current = current.next;
        }
        return result;
    }

    public String toString() {

        StringBuilder nodes = new StringBuilder();

        Node node = first;

        while (node != null) {
            nodes.append(node.item).append("\n");
            node = node.next;
        }

        if(isEmpty()) {
            return "";
        } else {
            return nodes.toString().substring(0, nodes.toString().length());
        }
    }
    class Queue{
        Node first, last;

        public void enqueue(Node n){
            if(first == null){
                first = n;
                last = first;
            }else{
                last.next = n;
                last = n;
            }
        }

        public Node dequeue(){
            if(first == null){
                return null;
            }else{
                Node temp = new Node(first);
                first = first.next;
                return temp;
            }
        }
    }


    public static void main(String[] args)
    {
        stackReversal s = new stackReversal();
        Scanner input = new Scanner(System.in);
        System.out.print("Enter strings:");
        String in = "";
        while (!in.equals("end-of-input"))
        {
            in = input.nextLine();
            if (in.equals("end-of-input"))
                break;
            else
                s.push(in);
        }

        System.out.println("Strings:"+"\n" + s);
    }
}
4

1 に答える 1

1

上記のように修正しました。ロジックを逆にしています。元の Scanner メソッドは正しくフォーマットされていませんでした。

import java.util.*;

public class stackReversal {

    private class Node {
        private String item;
        private Node next;
       // private Node prev;
    }

    private Node first = null;

    public boolean isEmpty() {
        return (first == null);
    }

    public void push(String s) {
        Node node = new Node();
        node.item = s;
        node.next = first;

        first = node;
    }

    public String pop() {
        if (first == null)
            throw new RuntimeException("Stack Empty!");
        String result = first.item;
        first = first.next;
        return result;

    }

    public String popString() {
        String result = "";
        Node current = first;

        while (current != null) {
            result += current.item;
            current = current.next;
        }
        return result;
    }

    public String toString() {

        StringBuilder nodes = new StringBuilder();

        Node node = first;



        while (node != null) {
            nodes.append(node.item).append("\n");
            node = node.next;
        }

        if(isEmpty()) {
            return "";
        } else {
            return nodes.toString().substring(0, nodes.toString().length());
        }
    }
    class Queue{
        Node first, last;

        public void enqueue(String s){
            Node node = new Node();
            node.item = s;
            node.next = first;

            first = node;
        }

        public Node dequeue(){
            if(first == null){
                return null;
            }else{
                Node temp = new Node();//Node temp = new Node();
                first = first.next;
                return temp;
            }
        }
        public String toString() {

            StringBuilder nodes = new StringBuilder();

            Node node = first;

            while (node != null) {
                // Insert the current item at the beginning of the String
                nodes.insert(0, String.format("%s%n", node.item));
                node = node.next;
            }



            if(isEmpty()) {
                return "";
            } else {
                return nodes.toString().substring(0, nodes.toString().length());
            }
        }

    }


    public static void main(String[] args)
    {
        stackReversal s = new stackReversal();
        Queue q = s.new Queue();
        Scanner input = new Scanner(System.in);
        System.out.print("Enter strings:");
        String in = input.nextLine();
        while (!in.equals("end-of-input"))
        {

            if (in.equals("end-of-input"))
                break;
            else
                q.enqueue(in);
                s.push(in);
            in = input.nextLine();
        }


        System.out.println("Strings:"+"\n" + s);
        System.out.println("Strings:"+"\n" + q);
    }
}
于 2016-11-09T14:37:07.027 に答える