在给定位置搜索节点双链表

Question

I am trying to search for a node based on the position of the node in a doubly linked list. For example, if the list contains 1,2,3,4,5 and I want to get position 3, it will return positions data, which is 3. I was able to get the first and second position, but when I try any other position after the second, it only returns the second position. I am not sure what is wrong. Here is my code so far:

Insert Method

public void insertAtStart(String data)
    {
        Node ptr = new Node(data);
        if(head == null)
        {
            head = ptr;
            tail = head;
        }
        else
        {
            head.prev = ptr;
            ptr.next = head;
            head = ptr;
        }
        size++;
    }

Search Method

public Node searchAt(int pos)
    {
        Node found = head;

        if(isEmpty())
        {
            System.out.println("List is empty");
            return null;
        }

        if(pos == 1)
            return found;

        for(int i = 2; i <= size; i++)
        {
            if(i == pos)
            {
                found = head.next;
            }
        }
        return found;
    }

Test:

        doc.insertAtStart("1");
        doc.insertAtStart("2");
        doc.insertAtStart("3");
        doc.insertAtStart("4");
        doc.insertAtStart("5");

        doc.printReverse();
        Node newNode = doc.searchAt(4);
        System.out.println("Node" + newNode.data);

output:

1: 1
2: 2
3: 3
4: 4
5: 5
Node: 2

Answer 1

The problem is at this line:

found = head.next;

You always return the second element (and the first one works thanks to the first branch of your if statement).

You should instead run through the list and get the correct element.

Answer 2

Tweak the for loop a bit:

• Move one position in list every iteration

• Break loop when position is reached.

   for(int i = 2; i <= size; i++) { found = head.next; if(i == pos) { break; } }