Find parent node in binary tree from value in javascript

Question

I have the following tree structure:

class Binarytree {
  constructor(val) {
    this.val = val;
    this.left = null;
    this.right = null;
  }

  insertLeft(val) {
    this.left = val;
  }

  insertRight(val) {
    this.right = val;
  }
}

I'm trying to find a parent node from a node value. I created the function below:

const getParent = function(root, n, parent) {
  if (!root) return null;
  if (root.val === n) return parent;
  else {
    getParent(root.left, n, root);
    getParent(root.right, n, root);
  }
};

Here is my test case:

const tree = new BinaryTree(1);
const node2 = new BinaryTree(2);
const node3 = new BinaryTree(3);
const node4 = new BinaryTree(4);
const node5 = new BinaryTree(5);
node2.insertRight(node4);
node3.insertRight(node5);
tree.insertLeft(node2);
tree.insertRight(node3);

const test = getParent(tree, 4, tree);

It is always returning null.

Nina Scholz · Accepted Answer · 2020-07-08 15:23:14Z

1

You need to return the nested call of getParent. You could chain the calls with logical OR ||.

class BinaryTree {
    constructor(val) {
        this.val = val;
        this.left = null;
        this.right = null;
    }

    insertLeft(val) {
        this.left = val;
    }

    insertRight(val) {
        this.right = val;
    }
}

const getParent = function(root, n, parent) {
    if (!root) return null;
    if (root.val === n) return parent;
    // return and chain with logical OR
    return getParent(root.left, n, root) || getParent(root.right, n, root);
}


const tree = new BinaryTree(1);
const node2 = new BinaryTree(2);
const node3 = new BinaryTree(3);
const node4 = new BinaryTree(4);
const node5 = new BinaryTree(5);
node2.insertRight(node4);
node3.insertRight(node5);
tree.insertLeft(node2);
tree.insertRight(node3);

const test = getParent(tree, 4, tree);
console.log(test);

edited Jul 8, 2020 at 15:23

answered Jul 8, 2020 at 15:17

Nina Scholz

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1 Comment

myTest532 myTest532 Over a year ago

Thank you! I need to return the first one (left or right) that is not null.

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