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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?Hash Functions 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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Challenge 7: Next Greater Element using Stack

Challenge 7: Next Greater Element using Stack

Try to solve the Next Greater Element Using a Stack problem.

Statement

Implement a nextGreaterElement() function that takes an array of integers, arr, as input and returns the next greater number for every element in the array.

The next greater number for a number arr[i] is the first number to its right that is greater than arr[i]. If no such number exists, return -1 for this number.

Constraints:

$1 \leq$

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