Good afternoon! Here's our prompt for today.

Assume we're using a binary tree in writing a video game via Binary Space Partitioning. We need to identify the bottom left leaf, that is-- the leftmost value in the lowest row of the binary tree.

In this example, the bottom left leaf is 3:

1/*
2    4
3   / \
4  3   5
5*/

Assuming the standard node definition of:

1function Node(val) {
2  this.val = val;
3  this.left = this.right = null;
4}

It would be called as such:

1const root = new Node(4);
2root.left = new Node(3);
3root.right = new Node(5);
4
5function bottomLeftNodeVal(root) { return; };
6bottomLeftNodeVal(root);
7// 3

Here's another example. Let's assume that there's at least the root node available in all binary trees passed as parameters.

1/*
2      4
3     / \
4    1   3
5       / \
6      5   9
7*/
8
9const root = new Node(4);
10root.left = new Node(1);
11root.right = new Node(3);
12root.right.left = new Node(5);
13root.right.right = new Node(9);
14
15bottomLeftNodeVal(root);
16// 5

Constraints

• Nodes in the binary tree <= 100000
• The values in the nodes will be in the range -1000000000 and 1000000000
• Expected time complexity : O(n)
• Expected space complexity : O(n)

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How do I practice this challenge?

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  console.log('PASSED: ' + 'assert.equal(bottomLeftNodeVal(tree4), 1);');

var assert = require('assert');

​

function Node(val) {

  this.val = val;

  this.left = this.right = null;

}

​

function bottomLeftNodeVal(root) {

  // Fill in this method

  return root;

}

​

// const root = new Node(4);

// root.left = new Node(1);

// root.right = new Node(3);

// root.right.left = new Node(5);

// root.right.right = new Node(9);

​

// console.log(bottomLeftNodeVal(root));

​

function Node(val) {

  this.val = val;

  this.left = null;

  this.right = null;

}

​

// Regular binary trees

var tree1 = new Node(4);

tree1.left = new Node(1);

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