Disjoint sets, also known as Union-Find data structures, are a foundational concept in computer science. They are used to solve problems related to grouping, connectivity, and partitioning efficiently. In this guide, we’ll break down the key components of disjoint sets, discuss optimizations, and explore their real-world applications. What Are Disjoint…
Unique Paths – 62. LeetCode
The Unique Paths problem asks us to find the number of distinct ways to reach the bottom-right corner of a grid starting from the top-left corner. You can only move right or down at any step. This problem is a great example of combinatorics, recursion, and dynamic programming. Imagine you’re…
Subsets – 78. LeetCode
The Subsets problem is classic combinatorics tasks in which you’re given a list of unique integers, and your goal is to return all possible subsets of the list (including the empty subset of the list itself). It’s a fundamental problem that helps build a deeper understanding of recursion, backtracking, and…
Construct Quad Tree – 427. LeetCode
A Quad Tree is a tree data structure used to partition a 2D space into smaller regions for efficient representation and computation. In this problem, we are given a binary matrix and need to construct a Quad Tree where each node represents a region of the matrix. If all values…
Minimum Size Subarray Sum – 209. LeetCode
The Minimum Size Subarray Sum problem asks us to find the smallest contiguous subarray whose sum is greater than or equal to a given integer target. If no such subarray exists, we return 0. This problem is common in array manipulation and sliding window techniques. In simple terms, imagine you’re…
Invert Binary Tree – 226. LeetCode
Imagine you are looking at a family tree. If you flip it horizontally, the left children become right children and the right children become left children. This is exactly what the Invert Binary Tree problem asks us to do: swap all the left and right children of every node in…
Linked List Cycle II – 142. LeetCode
The Linked List Cycle II problem asks you to determine where a cycle begins in a linked list if one exists. A cycle occurs when a node in the list points back to a previous node, creating a loop. The task involves returning the starting node of the cycle or…
Design Linked List – 707. LeetCode
This problem asks you to design and implement your own linked list from scratch, either as a singly linked list or a doubly linked list, depending on your choice. Here’s a simplified explanation of the requirements: Tradeoffs Between Singly and Doubly Linked List 1. Singly Linked List: • Simpler to…
Reorder List – 143. LeetCode
In the “Reorder List” problem, you’re given a singly linked list, and the goal is to rearrange it such that the first element is followed by the last element, then the second element by the second-to-last, and so on. For example, given a list 1 -> 2 -> 3 ->…
Word Search – 79. LeetCode
The “Word Search” problem challenges you to determine if a word exists in a grid of letters. The word can be constructed by sequentially adjacent cells in the grid, where “adjacent” means horizontally or vertically neighboring. Each cell in the grid can be used only once per word. Imagine this…
