Question

  var m_root : Node = root
  private def insert(key: Int, value: Int): Node = {
        if(m_root == null) {
            m_root = Node(key, value, null, null)
        }
        var t : Node = m_root
        var flag : Int = 1
        while (t != null && flag == 1) {
            if(key == t.key) {
                t
            }
            else if(key < t.key) {
                if(t.left == null) {
                    t.left = Node(key, value, null, null)
                    flag = 0
                } else {
                    t = t.left
                }

            } else {
                if(t.right == null) {
                    t.right = Node(key, value, null, null)
                    flag = 0
                } else {
                    t = t.right
                }
            }
        }
      t
 }

I wrote iterative version insert a node to binary search tree. I want to terminate when node is created, but it doesn’t stop, because I think I didn’t assign terminating condition. How to I edit my code to terminate when a node inserted in?

Answer 1

I’m not sure exactly what behaviour you want, but the cause is quite clear.

Your loop is a while condition, which will loop until t is null. So while t is non-null the loop will continue.

You only ever assign t to non-null values – in fact you’re specifically checking for the null case and stopping it happening by creating a new node.

So either you need to reconsider your loop condition, or ensure t does in fact become null in some cases, depending on what your actual algorithm requirements are.

And since you’re returning t at the bottom, I suggest the while condition is wrong; the only possible way this could terminate is if t is null at this point, so it would be pointless to return this anyway.