BST Find Minimum Element in DSA Javascript - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a Binary Search Tree (BST)?

A BST is a tree where each node has at most two children. The left child's value is less than the parent's value, and the right child's value is greater. This helps in fast searching.

beginner

How do you find the minimum element in a BST?

Start at the root and keep moving to the left child until there is no left child. The last node you reach is the minimum element.

beginner

Why does moving left in a BST lead to the minimum element?

Because in a BST, left children always have smaller values than their parents, so the leftmost node holds the smallest value.

intermediate

What is the time complexity of finding the minimum element in a BST?

The time complexity is O(h), where h is the height of the tree. In the best case (balanced tree), it's O(log n), and in the worst case (skewed tree), it's O(n).

beginner

Show the JavaScript code snippet to find the minimum element in a BST.

function findMin(root) {
  if (!root) return null;
  while (root.left) {
    root = root.left;
  }
  return root.value;
}

In a BST, where is the minimum element located?

A At the leftmost node

B At the rightmost node

C At the root node

D At any leaf node

The minimum element is always at the leftmost node because left children have smaller values.

What should you do if the BST is empty when finding the minimum element?

A Throw an error

B Return the root value

C Return zero

D Return null or indicate no minimum

If the BST is empty (root is null), there is no minimum element, so return null.

What is the time complexity to find the minimum element in a balanced BST with n nodes?

A O(log n)

B O(n log n)

C O(1)

D O(n)

In a balanced BST, height h is about log n, so finding minimum takes O(log n) time.

Which of these steps is NOT part of finding the minimum element in a BST?

A Start at the root

B Keep moving to the right child

C Stop when no left child exists

D Return the last node's value

You move to the left child to find the minimum, not the right.

What does the function return if the BST has only one node?

A The value of the root's left child

B null

C The value of the single node

D Undefined

If there is only one node, it is the minimum, so the function returns its value.

Explain step-by-step how to find the minimum element in a Binary Search Tree.

Think about how BST organizes smaller values on the left.

Write a simple JavaScript function to find the minimum element in a BST and explain how it works.

Use a while loop to move left until no more left child.