Binary Search Tree Assign to Parent

Question

I have a question regarding the removing part from a binary search tree function.

switch (childCount){
    case 0: // It has no children then remove parent
        if(current.value < parent.value){
        parent.left = null;
        } else{
        parent.right = null;
        }
       break;
    case 1: //it has 1 children, reassign to parent
         if(current.value < parent.value){
         parent.left = (current.left === null ? current.right :   curent.left);
         } else {
        parent.right = (current.left === null ? current.right :   current.left);
         }  
        break;

I'm not really understanding case 1, and the values for parent.left AND parent.right. What does the (current.left === null ? current.right : curent.left) exactly mean? The syntax is throwing me off. I know it refers to a case that if it has one child, just reassign to the parent. But I'm still confused

Thanks,

See http://stackoverflow.com/questions/10323829/javascript-ternary-operator-example-with-functions — le_m, Jun 23 '16 at 15:20

score 2 · Accepted Answer · edited Jun 23 '16 at 15:24

2

parent.left = (current.left === null ? current.right : curent.left);

means

if (current.left === null)
    parent.left = current.right;
else
    parent.left = curent.left;

see for detail: Wikipedia - ternary operator

edited Jun 23 '16 at 15:24

le_m

19,302
9
64
74

answered Jun 23 '16 at 15:19

A.B.

2,374
3
24
40

Thank you, this make a lot of sense now! – Cesar Jun 23 '16 at 15:42

score 1 · Answer 2 · answered Jun 23 '16 at 15:25

So basically this is just saying that if the current node (the node we are trying to remove) has one and only one child we have to assign currents child to be a child of parent so we don't lose the child from the tree. As moller said, the assignments are ternary operators so if the test

parent.left = (current.left === null ? current.right : curent.left);

evaluates to true parent.left is set to current.right, otherwise it is set to current.left.

All these checks are to maintain the property of a binary search tree where left children are <= parent and right children are > than parent.

Binary Search Tree Assign to Parent

2 Answers2