链接列表（Java）中的逻辑错误插入节点

Question

I am trying to learn to insert a node in a linked list (and return the head), but for some reason it is not correct.

This is my approach:

1. Create the new node with the desired data

2. If we want to insert it in the beginning, point this new node to the head and return the new node

3. Otherwise, loop to the position where we want to insert the node

- Once we get there, point the node to be inserted's next to the current node's next

- Point the current node to the node to be inserted

- Return the head

Why does this not work? Thanks so much!

Node InsertNth(Node head, int data, int position) {
    Node node = new Node();
    node.data = data;

    if (position == 0) {
        node.next = head;
        return node;
    }
    else {
        Node curr = head;
        int currPos = 0;

        while (currPos < position) {
            curr = curr.next;
            currPos++;
        }
        node.next = curr.next;
        curr.next = node;
    }
    return head;
}

Answer 1

Given that you insert the new node after the curr node, this loop steps one node too far.

while (currPos < position) {
     curr = curr.next;
     currPos++;
}

You can easily work this out by stepping through through the code with a pen and paper, or with a debugger.

Answer 2

If you insert the node to the Head you need to set the Head to the node you're inserting.

Node InsertNth(Node head, int data, int position) {
Node node = new Node();
node.data = data;

if (position == 0) {
    node.next = head;
    head = node;
}
else {
    Node curr = head;
    int currPos = 0;

    while (currPos < position) {
        curr = curr.next;
        currPos++;
    }
    node.next = curr.next;
    curr.next = node;
}
return head;

}