Invert a Binary Tree

This is a famous question that is often asked in coding interviews.

 How to swap two numbers without using the third variable?

This is one of the oldest trick questions from a coding interview.

Remove duplicate nodes in an unsorted linked list

This is a very interesting coding question that is being asked a lot in coding interviews.

 Find all missing numbers in an array

This is a popular array-based coding problem. Given an array with a range 0 - n-1 - the goal is to find all missing elements, but considering that the array can contain duplicate elements also.

 Find the smallest and largest elements in an array

This is one very interesting question that is often asked in coding interviews.