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Data Structures

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Arrays

What is an Array?Two Dimensional Arrays Challenge 1: Remove Even Integers from an Array Solution Review: Remove Even Integers from an Array Challenge 2: Merge Two Sorted Arrays Solution Review: Merge Two Sorted Arrays Challenge 3: Find Two Numbers that Add up to "n"Solution Review: Find Two Numbers that Add up to "n"Challenge 4: Array of Products of All Elements Except Itself Solution Review: Array of Products of All Elements Except Itself Challenge 5: Find Minimum Value in Array Solution Review: Find Minimum Value in an Array Challenge 6: First Non-Repeating Integer in an Array Solution Review: First Non-Repeating Integer in an Array Challenge 7: Find Second Maximum Value in an Array Solution Review: Find Second Maximum Value in an Array Challenge 8: Right Rotate the Array by One Index Solution Review: Right Rotate the Array by One Index Challenge 9: Re-arrange Positive & Negative Values Solution Review: Re-arrange Positive & Negative Values Challenge 10: Rearrange Sorted Array in Max/Min Form Solution Review: Re-arrange Sorted Array in Max/Min Form Challenge 11: Find the Sum of Maximum Sum Subarray Solution Review: Find the Sum of Maximum Sum Subarray Array Interview Questions

Linked Lists

What is the Singly Linked List (SLL)?Basic Linked List Operations Insertion in a Singly Linked List Challenge 1: Insertion in a Singly Linked List (insert at End)Solution Review: Insertion in a Singly Linked List(insert at End)Insertion in Singly Linked List (Insert After)Challenge 2: Search in Singly Linked List Solution Review: Search in a Singly Linked List Singly Linked List Deletion (Implementation)Challenge 3: Deletion in Singly Linked List(Delete by Value)Solution Review: Deletion in Singly Linked List Linked Lists vs. Arrays What is a Doubly Linked List (DLL)?Linked List with Tail Challenge 4: Find the Length of a Linked List Solution Review: Find the Length of a Linked List Challenge 7: Find the Middle Node of a Linked List Solution Review: Find the Middle Node of a Linked List Challenge 8: Remove Duplicates from a Linked List Solution Review: Remove Duplicate from a Linked List Challenge 9: Union & Intersection of Lists Solution Review: Union & Intersection of Lists Challenge 10: Return the Nth node from End Solution Review: Return the Nth node from End Challenge 11: Find if Doubly Linked-list is a Palindrome Solution: Find if a Doubly Linked-list is a Palindrome Linked list Interview Questions

Stack/Queues

What is a Stack?Stack (Implementation)What is a Queue?Queue (Implementation)Challenge 1: Generate Binary Numbers from 1 to n using a Queue Solution Review: Generate Binary Numbers from 1 to n using Queue Challenge 2: Implement Two Stacks using one Array Solution Review: Implement Two Stacks using one Array Challenge 3: Reversing the First k Elements of a Queue Solution Review: Reversing the First k Elements of a Queue Challenge 4: Implement Queue using Stack Solution Review: Implement Queue using Stack Challenge 5: Sort the Values in a Stack Solution Review: Sort the Values in a Stack Challenge 6: Evaluate Postfix Expressions using Stacks Solution Review: Evaluate Postfix Expressions using Stacks Challenge 7: Next Greater Element using Stack Solution Review: Next Greater Element using Stack Challenge 8: Solve a Celebrity Problem using a Stack Solution Review: Solve a Celebrity Problem using a Stack Challenge 9: Check for Balanced Parentheses using a Stack Solution Review: Check for Balanced Parentheses using a Stack Challenge 10: Create Stack where min() gives minimum in O(1)Solution Review: Create Stack where min() gives minimum in O(1)Stack/Queue Interview Questions

Graphs

What is a Graph?Representation of Graphs Graph Implementation Complexities of Graph Operations What is a Bipartite Graph?Graph Traversal Algorithms Challenge 1: Implement Breadth First Search Solution Review: Implement Breadth First Search Challenge 2: Implement Depth First Search Solution Review: Implement Depth First Search Challenge 3: Cycle Detection in a Directed Graph Solution Review: Cycle Detection in a Directed Graph Challenge 4: Find "Mother Vertex" in a Directed Graph Solution Review: Find "Mother Vertex" in a Directed Graph Challenge 5: Count the Number of Edges in an Undirected Graph Solution Review: Count the number of Edges in an Undirected Graph Challenge 6: Check if a Path Exists Between Two Vertices Solution Review: Check if a Path Exists Between Two Vertices Challenge 7: Check if a Directed Graph is Tree or not Solution Review: Check if a Directed Graph is Tree or not Challenge 8: Find Length of Shortest Path between Two Vertices Solution Review: Find the Shortest Path between Two Vertices Challenge 9: Remove Edge from a Directed Graph Solution Review: Remove Edge from a Directed Graph Graph Interview Questions

Trees

What is a Tree?Types of Trees What Makes a Tree Balanced?What is a Binary Tree?More on Complete Binary Trees Skewed Binary Tree What is a Binary Search Tree (BST)?Insertion in Binary Search Trees Insertion in BST (Complete Implementation)Search in Binary Search Trees (Implementation)Deletion in Binary Search Trees Deletion in Binary Search Trees (Implementation)Pre-Order Traversal in Binary Search Trees In-Order Traversal in Binary Search Trees Post-Order Traversal in Binary Search Tree What is an AVL Tree?AVL Insertion AVL Deletion What is a Red-Black Tree?Red-Black Tree Insertion Red-Black Tree Deletion What is a 2-3 Tree?2-3 Insertion 2-3 Deletion (Case #1)2-3 Deletion (Case #2)2-3-4 Trees Overview of Trees Challenge 1: Find the Minimum Value in a Binary Search Tree Solution Review: Find the Minimum Value in a Binary Search Tree Challenge 2: Find kth Maximum Value in a Binary Search Tree Solution Review: Find kth Maximum Value in a Binary Search Tree Challenge 3: Find Ancestors of Given Node in Binary Search Tree Solution Review: Find Ancestors of a Given Node in a BST Challenge 4: Find the Height of a Binary Search Tree Solution Review: Find the Height of a Binary Search Tree Challenge 5: Find Nodes at "k" Distance from the Root Solution Review: Find Nodes at "k" Distance from the Root Tree Interview Questions

Trie (Advanced Trees)

What is a Trie?The Structure of a Trie Insertion in a Trie Search in a Trie Deletion in a Trie Challenge 1: Total Number of Words in a Trie Solution Review: Total Number of Words in a Trie Challenge 2: Find All of the Words in a Trie Solution Review: Find All of the Words in a Trie Challenge 3: Sort the Elements of an Array using a Trie.Solution Review: Sort the Elements of an Array using a Trie.Challenge 4: Word Formation from a Given Dictionary using a Trie Solution Review: Word Formation from Given Dictionary using Trie Trie Interview Questions

Heaps

What is a Heap Why Use Heaps?Heap Representation in Arrays Max Heap: Introduction Max Heap (Implementation)Min Heap: An Introduction Min Heap (Implementation)Challenge 1: Convert a Max-Heap to a Min-Heap Solution Review: Convert a Max-Heap to a Min-Heap Challenge 2: Find the k Smallest Elements in an Array Solution Review: Find the k Smallest Elements in an Array Challenge 3: Find the k Largest Elements in an Array Solution Review: Find the k Largest Elements in an Array Heap Interview Questions

Hash Tables

What is a Hash Table?

Collisions in Hash Tables

Building a Hash Table from Scratch

Add/Remove & Search in a Hash Table (Implementation)

Complete Implementation of Hash Tables

Trie vs Hash Table

HashMap vs HashSet

Challenge 1: Find whether an array is a subset of another array

Solution Review: Find whether an array is a subset of another array

Challenge 2: Check if the given arrays are disjoint

Solution Review: Check if the given arrays are disjoint

Challenge 3: Find symmetric pairs in an Array

Solution Review: Find symmetric pairs in an Array

Challenge 4: Trace the complete path of a journey

Solution Review: Trace the complete path of a journey

Challenge 5: Find two pairs in an Array such that a+b = c+d

Solution Review: Find two pairs in an Array such that a+b = c+d

Challenge 6: Find If a Subarray with a Sum Equal to 0 Exists

Solution Review: Find if a subarray with a sum equal to 0 exists.

Challenge 7: First Non-Repeating Integer in an Array

Solution Review: First Non-Repeating Integer in an Array

Challenge 8: Remove Duplicate from a Linked List using Hashing

Solution Review: Remove Duplicate from Linked List using Hashing

Challenge 9: Union and Intersection of Lists using Hashing

Solution Review: Union and Intersection of Lists using Hashing

Challenge 10: Find Two Numbers that Add up to "n"

Solution Review: Find Two Numbers that Add up to "n"

Hashing Interview Questions

Conclusion

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Solution Review: Find symmetric pairs in an Array

Solution Review: Find symmetric pairs in an Array

Let’s solve the Find Symmetric Pairs in an Array problem.

Statement

Given an array of pairs, nums, find all the symmetric pairsBy definition, (a, b) and (c, d) are symmetric pairs iff, a = d and b = c. from it. If no symmetric pair is found, return an empty array.

Constraints:

$2 \leq$ nums.length $\leq10^3$
nums[i].length ...