两部分，在Java中删除最后一个元素并替换节点中的两个元素

Question

I'm working a linkedlist from my assignment, one part is to remove the last element from the list, the other part is to replace one element with a new one in the linked list.

I actually struggled to figure out how to put it together, I did some research on removing and replacing, and the result was not really helpful but there was one that is strongly related to replace.

 public boolean replace(int element, int index) {
        Node cursor = first;
        Node prev = null;

        while (cursor != null && index >= 0) {
            index--;
            prev = cursor;
            cursor = cursor.next;
        }

        if (index > 0) return false;

        if (prev != null)
            prev.element = element;

        return true;
    }

but my assignment was specific about not using boolen, but using public void replace(int oldVal, int newVal)

the other part about replacing is like this

/*********************************
// public void replace(int oldVal, int newVal)
// —replaces all occurrences of oldVal in the list with newVal.
//********************************

    public void replace(int oldVal, int newVal)
    {
          IntNode oldval = new IntNode(oldVal,front);
        IntNode newval = new IntNode(newVal,front);

        if (front == null)
        {
            front = newval;
        }
        else
            while (oldval.next != null)
            {
                oldval = oldval.next;
                oldval.next = newval;
            }

    }

Updated, still struggling if the code is correct to allow me to change one element with a new element in the linked list.

 public IntNode(int val, IntNode next)
       {
           this.val = val;
           this.next = next;
       }

unless I am mistaken and that I dont need to use it.

the result shoudl be allowing me to remove a element from the end of the list, and to be able to replace a old value with a new one.

Answer 1

Assuming your node's .next is working correctly your removeLast should look something like this:

public void removeLast()
{
    if (front != null && front.next != null)
    {
        IntNode secondtolast = front;
        while (secondtolast.next.next != null)
        {
            secondtolast = secondtolast.next;
        }
        secondtolast.next = null;
    }
}

Based on the description of your replace() function, you are not going to be replacing nodes but rather the values of the nodes.

public void replace(int oldVal, int newVal)
{
    while (front.next != null)
    {
        if (front.val == oldVal)
        {
            front.val = newVal;
        }
        front = front.next;
    } 
}