Closest Common Ancestor in Binary Tree Coding Interview Question | Skilled.dev
Interview Question

Closest Common Ancestor in Binary Tree

Given two values in a binary tree, write a function findClosestAncestor that finds the closest ancestor node relative to these target nodes.

You will be given a root as the input along with the values of two nodes that exist in the tree. The tree contains only unique integers, and the child values will always be different.

It's important to note that this is a binary tree and not a BST where the value of the node could indicate its position as an ancestor or where to search for the children.

       9
      / \
     5   4
    / \   \
   1   7   3
  / \       \
 42  10      2

findClosestAncestor(root, 10, 7); // 5

The tree nodes will use the following implementation:

class BinaryNode {
  constructor(data) {
    this.data = data;
    this.left = null;
    this.right = null;
  }
}

Breakdown

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Table of Contents

Validate My Answer

  1. This can be solved iteratively or recursively. Let's go ahead and assume you don't need to worry about stack overflows if you're interested in solving it recursively. That's the solution I'll be showing.

  2. A node can be the common ancestor with itself and a child node.

  3. At worst, the root is the common ancestor for all nodes.

  4. This can be solved in O(n) time and space.

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Table of Contents

Test Results

Run your code and see results here...

const findClosestAncestor = (root, firstChildValue, secondChildValue) => {
  // Your solution here
}
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Closest Common Ancestor in Binary Tree

Given two values in a binary tree, write a function findClosestAncestor that finds the closest ancestor node relative to these target nodes.

You will be given a root as the input along with the values of two nodes that exist in the tree. The tree contains only unique integers, and the child values will always be different.

It's important to note that this is a binary tree and not a BST where the value of the node could indicate its position as an ancestor or where to search for the children.

       9
      / \
     5   4
    / \   \
   1   7   3
  / \       \
 42  10      2

findClosestAncestor(root, 10, 7); // 5

The tree nodes will use the following implementation:

class BinaryNode {
  constructor(data) {
    this.data = data;
    this.left = null;
    this.right = null;
  }
}
const findClosestAncestor = (root, firstChildValue, secondChildValue) => {
  // Your solution here
}
// Upgrade for full course access
// Upgrade for full course access