[Hamill] feat : DoublyLinkedList 구현

Author: hanurii

hamill/.gradle/5.2.1/executionHistory/executionHistory.bin

@@ -0,0 +1,257 @@
+package com.codesquad.datastructurestudy.linkedlist;
+
+/**
+ * This class implements a DoublyLinkedList. This is done using the classes
+ * LinkedList and Link.
+ *
+ * A linked list is similar to an array, it holds values. However,
+ * links in a linked list do not have indexes. With a linked list
+ * you do not need to predetermine it's size as it grows and shrinks
+ * as it is edited. This is an example of a double ended, doubly
+ * linked list. Each link references the next link and the previous
+ * one.
+ *
+ * 연결 리스트는 배열과 유사하며, 값을 가지고 있다. 그러나 연결 리스트의 링크에는
+ * 인덱스가 없다. 연결 리스트를 사용하면 편집할 때 크기가 커지거나 작아지는 것을
+ * 미리 파악할 필요가 없다. 이것은 이중 말단, 이중 연결 리스트의 예다. 각 링크는
+ * 다음 링크와 이전 링크를 참조한다.
+ *
+ */
+
+public class DoublyLinkedList {
+    /**
+     * Head refers to the front of the list
+     * 헤드는 목록 앞쪽을 가리킨다
+     */
+    private Link head;
+
+    /**
+     * Tail refers to the back of the list
+     * 테일은 목록 뒤쪽을 가리킨다
+     */
+    private Link tail;
+
+    /**
+     * Default Constructor
+     */
+    public DoublyLinkedList() {
+        head = null;
+        tail = null;
+    }
+
+    /**
+     * Constructs a list containing the elements of the array
+     * 배열의 요소를 포함하는 포함하는 리스트 구성
+     *
+     * @param array the array whose elements are to be placed into this list
+     * @throws NullPointerException if the specified collection is null
+     *
+     * array : 이 리스트에 요소를 넣을 배열
+     * 만약 지정된 콜렉션이 null이면 NullPointerException을 throws 해라
+     */
+    public DoublyLinkedList(int[] array) {
+        if (array == null) throw new NullPointerException();
+        for (int i : array) {
+            insertTail(i);
+        }
+    }
+
+    /**
+     * Insert an element at the head
+     * 머리 부분에 element 삽입
+     *
+     * @param x Element to be inserted
+     * 삽입할 element x
+     */
+    public void insertHead(int x) {
+        Link newLink = new Link(x); // Create a new link with a value attached to it
+        if (isEmpty()) // Set the first element added to be the tail
+            tail = newLink;
+        else
+            head.previous = newLink; // newLink <-- currentHead(head)
+        newLink.next = head; // newLink <--> currentHead(head)
+        head = newLink; // newLink(head) <--> oldHead
+    }
+
+    /**
+     * Insert an element at the tail
+     *
+     * @param x Element to be inserted
+     *
+     */
+    public void insertTail(int x) {
+        Link newLink = new Link(x);
+        newLink.next = null; // currentTail(tail)  newLink -->
+        if (isEmpty()) { // Check if there are no elements in list then it adds first element
+            tail = newLink;
+            head = tail;
+        } else {
+            tail.next = newLink; // currentTail(tail) --> newLink -->
+            newLink.previous = tail; // currentTail(tail) <--> newLink -->
+            tail = newLink; // oldTail <--> newLink(tail) -->
+        }
+    }
+
+    /**
+     * Delete the element at the head
+     *
+     * @return The new head
+     */
+    public Link deleteHead() {
+        Link temp = head;
+        head = head.next; // oldHead <--> 2ndElement(head)
+        head.previous = null; // oldHead --> 2ndElement(head) nothing pointing at lod head so will be removed
+        if (head == null)
+            tail = null;
+        return temp;
+    }
+
+    /**
+     * Delete the element at the tail
+     *
+     * @return The new tail
+     */
+    public Link deleteTail() {
+        Link temp = tail;
+        tail = tail.previous; // 2ndLast(tail) <--> oldTail --> null
+        tail.next = null; // 2ndLast(tail) --> null
+        if (tail == null) {
+            head = null;
+        }
+        return temp;
+    }
+
+    /**
+     * Delete the element from somewhere in the list
+     *
+     * @param x element to be deleted
+     * @return Link deleted
+     */
+    public void delete(int x) {
+        Link current = head;
+
+        while (current.value != x) {
+            if (current != tail) {
+                current = current.next;
+            } else {
+                throw new RuntimeException("The element to be deleted does not exist!");
+            }
+        }
+
+        if (current == head)
+            deleteHead();
+        else if (current == tail)
+            deleteTail();
+        else {
+            current.previous.next = current.next;
+            current.next.previous = current.previous;
+        }
+    }
+
+    /**
+     * Inserts element and reorders
+     *
+     * @param x Element to be added
+     */
+    public void insertOrdered(int x) {
+        Link newLink = new Link(x);
+        Link current = head;
+        while (current != null && x > current.value)
+            current = current.next;
+
+        if (current == head)
+            insertHead(x);
+
+        else if (current == null)
+            insertTail(x);
+
+        else {
+            newLink.previous = current.previous;
+            current.previous.next = newLink;
+            newLink.next = current;
+
+        }
+    }
+
+    /**
+     * Returns true if list is empty
+     * 리스트가 비어있으면 true를 반환한다
+     *
+     * @return true if list is empty
+     *
+     */
+    public boolean isEmpty() {
+        return (head == null);
+    }
+
+    /**
+     * Prints contents of the list
+     * 리스트 내용 출력
+     */
+    public void display() {
+        Link current = head;
+        while (current != null) {
+            current.displayLink();
+            current = current.next;
+        }
+        System.out.println();
+    }
+}
+
+class Link {
+    /**
+     * Value of node
+     */
+    public int value;
+    /**
+     * This points to the link in front of the new link
+     */
+    public Link next;
+    /**
+     * This points to the link behind the new link
+     */
+    public Link previous;
+
+    /**
+     * Constructor
+     *
+     * @param value Value of node
+     */
+    public Link(int value) {
+        this.value = value;
+    }
+
+    /**
+     * Displays the node
+     */
+    public void displayLink() {
+        System.out.print(value + " ");
+    }
+
+    /**
+     * Main Method
+     *
+     * @param args Command line arguments
+     */
+    public static void main(String[] args) {
+        DoublyLinkedList myList = new DoublyLinkedList();
+        myList.insertHead(13);
+        myList.insertHead(7);
+        myList.insertHead(10);
+        myList.display();
+
+        myList.insertTail(11);
+        myList.display();
+
+        myList.deleteTail();
+        myList.display();
+
+        myList.delete(7);
+        myList.display();
+
+        myList.insertOrdered(23);
+        myList.insertOrdered(67);
+        myList.insertOrdered(3);
+        myList.display();
+    }
+}