1. head insertion
public void addFirst(int data) { //Head insertion DLinkedNode newNode = new DLinkedNode(data);//New nodes joined DLinkedNode next = head.next; newNode.next = next; next.prev = newNode; head.next = newNode; newNode.prev = head; }
2. tail insertion method
public void addLast(int data) {//Tail insertion DLinkedNode newNode = new DLinkedNode(data);//Newly inserted node DLinkedNode prev = head.prev; newNode.next = head; head.prev = newNode; newNode.prev = prev; prev.next = newNode; }
3. Insert anywhere, the first data node is subscript 0
public void addIndex(int index,int data) {//Insert anywhere int size = size(); if(index < 0 || index > size){ return; } if(index == 0){ addFirst(data); return; } if(index == size) { addLast(data); return; } DLinkedNode next = getPos(index); DLinkedNode prev = next.prev; DLinkedNode newNode = new DLinkedNode(data); prev.next = newNode; newNode.prev = prev; next.prev = newNode; newNode.next = next; }
The method used here to calculate the length of the linked list:
public int size(){ int size = 0; for(DLinkedNode cur = head.next; cur != head; cur = cur.next) { size++; } return size; }
And find a location in the linked list:
public DLinkedNode getPos(int index) { DLinkedNode cur = head.next; for(int i = 0; i < index; i++){ cur = cur.next; } return cur; }
4. Check whether the keyword key is in the linked list
public boolean contains(int key) {//Find the node containing the key for(DLinkedNode cur = head.next; cur != head; cur = cur.next) { if(cur.val == key){ return true; } } return false; }
5. Delete the node with the first key
public void remove(int key){ DLinkedNode toRemove = find(key); if(toRemove == null) { return; } DLinkedNode prev = toRemove.prev; DLinkedNode next = toRemove.next; prev.next = next; next.prev = prev; }
Here we use the method to find the position of key in the linked list:
public DLinkedNode find(int key) { for(DLinkedNode cur = head.next; cur != head; cur = cur.next) { if(cur.val == key){ return cur; } } return null; }
6. Delete all nodes whose value is key
public void removeAll(int key){ while (true){ DLinkedNode toRmove = find(key); if(toRmove == null){ return; } DLinkedNode prev = toRmove.prev; DLinkedNode next = toRmove.next; prev.next = next; next.prev = prev; } }
7. Print the linked list
public void display(){ System.out.print("Forward:["); for(DLinkedNode cur = head.next; cur != head; cur = cur.next){ System.out.print(cur.val); if(cur.next != head){ System.out.print(","); } } System.out.println("]"); System.out.println("reverse:["); for(DLinkedNode cur = head.prev; cur != head; cur = cur.prev){ System.out.print(cur.val); if(cur.prev != head){ System.out.print(","); } } System.out.println("]"); }
8. Clear the list
public void clear(){ head.next = head; head.prev = head; }