Data-Structures

Trees are one of the most important data structures for coding interviews. They appear in about 20-25% of all interview questions at top tech companies. If you are comfortable with trees, you have a big advantage. In this article, you will learn binary trees, tree traversals, and binary search trees (BST). We show every example in Kotlin, Python, and Go. What is a Tree? A tree is a hierarchical data structure made of nodes connected by edges. It looks like an upside-down tree — the root is at the top, and the leaves are at the bottom. ...

Hash maps are the most useful data structure for coding interviews. If you can only master one data structure beyond arrays, make it hash maps. They give you O(1) average-time lookups, insertions, and deletions. Many interview problems that seem hard become easy once you use a hash map. In this article, you will learn how hashing works, when to use hash maps vs hash sets, and how to solve classic interview problems. We show every example in Kotlin, Python, and Go. ...

Stacks and queues are two of the most fundamental data structures in computer science. They are building blocks for many algorithms and appear frequently in coding interviews. The rules are simple — stacks follow Last In, First Out (LIFO), and queues follow First In, First Out (FIFO). In this article, you will learn how stacks and queues work, how to implement them, and how to solve classic interview problems. We show every example in Kotlin, Python, and Go. ...

Linked lists are the second most common data structure in coding interviews after arrays. They test your ability to work with pointers, handle edge cases, and think about memory. In this article, you will learn how linked lists work, how to implement them, and how to solve classic interview problems. We show every example in Kotlin, Python, and Go. What is a Linked List? A linked list is a collection of nodes. Each node stores two things: a value and a pointer (reference) to the next node. Unlike arrays, linked list nodes are not stored next to each other in memory. They can be anywhere in memory, connected through pointers. ...

Arrays and strings are the most common data structures in coding interviews. Almost every technical interview at Google, Meta, Amazon, or any tech company starts with an array or string problem. If you want to pass coding interviews, you need to master these two first. In this article, you will learn what arrays and strings are, their time complexities, and how to solve classic interview problems. We show every example in Kotlin, Python, and Go. ...

In the previous tutorial, we learned about functions. Now let’s learn about Python’s built-in data structures: lists, dictionaries, sets, and tuples. These are the tools you use every day in Python. By the end of this tutorial, you will know how to store, access, and transform collections of data. Lists A list is an ordered, mutable collection. You can add, remove, and change items. fruits = ["apple", "banana", "cherry"] print(fruits[0]) # apple — first item print(fruits[-1]) # cherry — last item print(len(fruits)) # 3 Adding Items fruits.append("date") # Add to end: ["apple", "banana", "cherry", "date"] fruits.insert(1, "avocado") # Insert at index 1: ["apple", "avocado", "banana", ...] fruits.extend(["fig", "grape"]) # Add multiple items to end Removing Items fruits.remove("banana") # Remove by value (first occurrence) last = fruits.pop() # Remove and return last item item = fruits.pop(0) # Remove and return item at index 0 List Slicing Slicing creates a new list from part of an existing list. The syntax is list[start:end:step]: ...