How to sum the three values using recursion - Javascript

Question

Write a function that returns the sum of all nodes, including root

var nodes = {
  value: 7,
  left: { value: 1, left: null, right: null },
  right: { value: 4, left: null, right: null }
};

Considering this, result should be equal to 12.

sumTheTreeValues = root => {
  console.log(root.value);
  if (root.left != null) {
    sumTheTreeValues(root.left);
  }
  if (root.right != null) {
    sumTheTreeValues(root.right);
  }
};

If this code will log

7
1
4

How to return the sum of these numbers without having to pass new parameter ?

Start by trying to return a value instead of logging it... — Bergi
– Bergi, Commented Mar 31, 2018 at 20:47

Ori Drori · Accepted Answer · 2018-03-31 19:06:20Z

2

Add the left and right nodes value to the current value and return:

var nodes = {
  value: 7,
  left: { value: 1, left: null, right: null },
  right: { value: 4, left: null, right: null }
};

sumTheTreeValues = root => {
  let value = root.value;

  if (root.left != null) {
    value += sumTheTreeValues(root.left);
  }
  if (root.right != null) {
    value += sumTheTreeValues(root.right);
  }
  
  return value;
};

console.log(sumTheTreeValues(nodes));

You can also shorten it up a bit because null is automatically casted to 0 when added to a number:

var nodes = {
  value: 7,
  left: { value: 1, left: null, right: null },
  right: { value: 4, left: null, right: null }
};

sumTheTreeValues = root => root.value + 
  (root.left && sumTheTreeValues(root.left)) + 
  (root.right && sumTheTreeValues(root.right));

console.log(sumTheTreeValues(nodes));

edited Mar 31, 2018 at 19:06

answered Mar 31, 2018 at 19:02

Ori Drori

196k32 gold badges243 silver badges233 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Stefan Octavian · Accepted Answer · 2018-03-31 19:05:51Z

-1

Another way is to wrap your function inside another:

 function sum(root) {
    var result = 0;
    var sumTheTreeValues = root => {
       result += root.value
       if (root.left != null) {
          sumTheTreeValues(root.left);
        }
        if (root.right != null) {
           sumTheTreeValues(root.right);
        }
     };
     sumTheValues(root)
     return result;
 }

answered Mar 31, 2018 at 19:05

Stefan Octavian

6208 silver badges20 bronze badges

Collectives™ on Stack Overflow

How to sum the three values using recursion - Javascript

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related