CODEWITHSUNDEEP
javaloopslinked-listinfinite-loop
N0ob
N0ob

Reputation: 61

bug in single linked list reversion

Infinite loop in a singly linked list reversing algorithm. I tried to do the code on a piece of paper but still can't find the bug

    public void reverse ()
    {
    Node pointer = list;
    Node newList = new Node();
    Node temp = new Node();
    Node tempMoving = new Node();

    if (pointer != null)
    {
        newList = pointer;

        while (pointer.next != null)
        {
            System.out.println ("loop");
            temp = pointer;
            pointer = pointer.next;
            temp.next = pointer.next;
            tempMoving = pointer;
            tempMoving.next = newList;
            newList = tempMoving;
        }
    }

    list = newList;
    }

What I envisioned this algorithm to do is that when it moves to a new node, it takes that node and puts it into the beginning of a new list and it will keep repeating until it has reached the end. However, it only prints "loop" :(

Upvotes: 1

Views: 45

Answers (1)

Arvind Kumar Avinash
Arvind Kumar Avinash

Reputation: 79530

You can simply do it as follows:

public void reverse() {
    // Assuming `head` is the first node in linked list
    Node current = head, previous = null, forward = null;
    while (current.next != null) {
        forward = current.next;
        current.next = previous;
        previous = current;
        current = forward;
    }
    head = current;
    head.next = previous;
}

Upvotes: 1

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