Time Complexity

What is Big O Notation?

Big O notation describes how an algorithm’s running time or memory usage grows as the input size grows, focusing on the dominant term and ignoring constant fac…

Difference Between Array and Linked List

An array stores elements in contiguous memory with fixed-size, index-based access in O(1), while a linked list stores elements as nodes scattered in memory, ea…

What is a Hash Table?

A hash table is a data structure that maps keys to values using a hash function to compute an index into an array of buckets, giving average O(1) insertion, lo…

What is a Binary Search Tree (BST)?

A binary search tree is a binary tree where every node’s left subtree holds smaller keys and its right subtree holds larger keys, enabling search, insertion, a…

What is Dynamic Programming?

Dynamic programming is a technique for solving problems by breaking them into overlapping subproblems and storing each subproblem’s result so it is computed on…

What is a Heap?

A heap is a complete binary tree stored in an array that satisfies the heap property — in a min-heap every parent is smaller than or equal to its children, giv…

BFS vs DFS: What is the Difference?

BFS (breadth-first search) explores a graph level by level using a queue, while DFS (depth-first search) explores as deep as possible along one path before bac…

What is a Trie?

A trie, or prefix tree, is a tree-based data structure that stores strings character by character along shared paths, letting you search, insert, and check pre…

Merge Sort vs Quick Sort: What is the Difference?

Merge sort splits an array in half, recursively sorts both halves, then merges them, guaranteeing O(n log n) time and stability at the cost of O(n) extra space…

What is Binary Search?

Binary search is an algorithm that finds a target value in a sorted collection by repeatedly halving the search range, comparing the target to the middle eleme…

What is a Priority Queue?

A priority queue is an abstract data type where each element has a priority, and the element with the highest (or lowest) priority is always removed first, typ…

What is the Difference Between Time and Space Complexity?

Time complexity measures how the number of operations an algorithm performs grows with input size, while space complexity measures how the memory it needs grow…

What is a Balanced Tree?

A balanced tree is a binary tree structured so the height difference between subtrees at every node stays bounded (typically by a constant like 1), keeping the…

What is the Two Pointer Technique?

The two pointer technique uses two index variables that move through a data structure — typically a sorted array or a linked list — to solve problems in O(n) t…

What is the Sliding Window Technique?

The sliding window technique maintains a contiguous subrange of an array or string, expanding and contracting its boundaries as it scans, to solve subarray or…

What is Memoization?

Memoization is an optimization technique that caches the results of expensive function calls keyed by their arguments, so repeated calls with the same inputs r…

What is a Circular Queue?

A circular queue is a fixed-size queue implemented on an array where the last position wraps around to connect back to the first, allowing enqueue and dequeue…

What is Topological Sort?

Topological sort produces a linear ordering of the nodes in a directed acyclic graph such that for every directed edge from node A to node B, A appears before…

What is Heap Sort?

Heap sort builds a max-heap from the input array, then repeatedly swaps the root (the current maximum) with the last unsorted element and sifts the reduced hea…

What is Counting Sort?

Counting sort sorts integers by counting how many times each distinct value occurs, converting those counts into prefix sums that give each value its final pos…

What is Radix Sort?

Radix sort sorts integers (or fixed-length strings) by repeatedly applying a stable sort, usually counting sort, on one digit position at a time, moving from t…

What is Bucket Sort?

Bucket sort distributes elements from a roughly uniformly distributed input into a fixed number of buckets by value range, sorts each bucket individually with…

What is Insertion Sort?

Insertion sort builds the final sorted array one element at a time by taking each new element and shifting it leftward past every larger already-sorted element…

What is Selection Sort?

Selection sort repeatedly scans the unsorted portion of an array to find the minimum element and swaps it into place at the front, giving an O(n²) comparison-b…