K5kC Algo Kernel

Comprehensive 150 problems covering all major patterns and concepts

161 problems•19 sections

Problem	Difficulty	Video
Two Sum	easy
Isomorphic Strings	easy
Contains Duplicate 1 - Check if array has duplicates	easy
Valid Anagram	easy
Is Subsequence	easy
Valid Sudoku	medium	-
Group Anagrams	medium
Encode and Decode Strings	medium

Problem	Difficulty	Video
Valid Palindrome	easy
Backspace String Compare	easy	-
Container With Most Water	medium
3Sum0 - Find three elements in an array that sum to a zero	medium
Dutch National Flag DNF	medium
2Sum 2 – Input array is sorted	medium
Trapping Rain Water	hard	-

Problem	Difficulty	Video
Longest Substring Without Repeating Characters	medium
Longest Substring with Same Letters after Replacement	medium
Find anagrams of a string in another string	medium	-
Permutation in String	medium	-
Count Number of Nice Subarrays	medium	-
Minimum Window Substring	hard
Sliding Window Maximum	hard	-

Problem	Difficulty	Video
Product of Array Except Self	medium

Problem	Difficulty	Video
Largest Number From Given Numbers	medium
Kth Largest Element in an Array	medium	-
Sort Characters By Frequency	medium	-

Problem	Difficulty	Video
Valid Parentheses	easy
Implement stack using queues	easy	-
Implement Queue using Stacks	easy	-
Next Greater Element 1	easy	-
Evaluate Reverse Polish Notation	medium	-
Min Stack	medium	-
Daily Temperatures	medium	-
Car Fleet	medium	-
Koko Eating Bananas	medium	-
Online Stock Span	medium	-
Largest Rectangle in Histogram	hard	-

Problem	Difficulty	Video
Binary Search on Sorted Array	easy
Search in Rotated Sorted Array	medium
Search a 2D Matrix 1 - Elements sorted row-wise and first integer of each row is greater than last element of previous row is greater than last element of previous row	medium	-
Find Minimum in Rotated Sorted Array	medium
Time Based Key-Value Store	medium	-
Median of Two Sorted Arrays	hard	-

Problem	Difficulty	Video
Merge Two Sorted Linked Lists	easy
Linked List Cycle 1 - Detect Cycle	easy
Reverse Linked List	easy
Add Two Numbers represented as Linked List in Reversed Order	medium	-
Remove Nth Node From End of List	medium
Copy List with Random Pointer	medium	-
Reorder List such that i-th element points to n-i-th element	medium
Design LRU Cache	medium	-
Find Duplicate Number in array containing n+1 numbers between 1 and n	medium	-
K Reverse a linked list	hard	-

Problem	Difficulty	Video
Same Tree	easy
Maximum Depth of Binary Tree	easy
Balanced Binary Tree	easy	-
Invert Binary Tree	easy
Diameter Of a Binary Tree	easy	-
Subtree of Another Tree	easy
Validate Binary Search Tree	medium
Binary Tree Level Order Traversal - Level by Level	medium
Construct Binary Tree from Inorder and Preorder Traversal	medium
Binary Tree Right Side View	medium	-
Kth Smallest Element in a BST	medium
Lowest Common Ancestor of a Binary Search Tree	medium
Replace Words	medium	-
Binary Tree Path Sum - Maximum between any two nodes	hard
Serialize and Deserialize Binary Tree	hard

Problem	Difficulty	Video
Implement Trie	medium
Design Add and Search Words Data Structure	medium
Word Search 2 - Return All Words	hard

Problem	Difficulty	Video
Kth Largest Element in a Stream	easy
Last Stone Weight	easy	-
Top K Frequent Elements	medium
Design Twitter (Data Structure Design)	medium	-
Task Scheduler	medium	-
K closest Points to Origin	medium	-
Merge K Sorted Lists	hard
Find Median from Data Stream	hard

Problem	Difficulty	Video
Letter Combinations of a Phone Number	medium	-
Combination Sum 1	medium
Combination Sum 2 - Cant Reuse same element	medium	-
Permutations of Array 1	medium	-
Subsets 1	medium
Word Search 1 - Find if word exists	medium
Subsets 2	medium	-
Palindrome Partitioning	medium
N-Queens	hard	-

Problem	Difficulty	Video
Rotting Oranges	medium	-
Longest Consecutive Sequence	medium
Surrounded Regions	medium	-
Clone Undirected Graph	medium
Number of Islands	medium
Course Schedule 1 - Is it Possible	medium
Course Schedule 2 - Get Ordered Courses	medium	-
Graph Valid Tree	medium	-
Walls and Gates	medium	-
Pacific Atlantic Water Flow	medium	-
Max Area of Island	medium	-
Network Delay Time	medium	-
Cheapest Flights Within K Stops Problem	medium	-
Min Cost to Connect All Points	medium	-
Word Ladder 1 - Get Ladder Length	hard	-
Alien Dictionary	hard	-
Reconstruct Itinerary	hard	-
Swim in Rising Water	hard	-

Problem	Difficulty	Video
Climbing Stairs - Take atmost 2 Steps	easy
Best Time To Buy And Sell Stock 1 - only one transaction	easy
Min Cost Climbing Stairs	easy	-
Longest Palindromic Substring	medium
Maximum Subarray Sum	medium
Unique Paths in Grid 1 - Count all paths moving right or down	medium
Edit Distance	medium	-
Decode Ways	medium
Interleaving String	medium	-
Word Break 1 - Check if word is breakable	medium
Maximum Product Subarray	medium
House Robber	medium
House Robber 2 - Houses in circle	medium
Longest Increasing Subsequence	medium
Best Time To Buy And Sell Stock With Cooldown	medium	-
Coin Change with Fewest Number of Coins Given Infinite Supply	medium
Partition Equal Subset Sum	medium	-
Target Sum	medium
Palindromic Substrings	medium
Longest Common Subsequence LCS 1 - Get Length	medium
Regular Expression Matching	hard	-
Distinct Subsequences	hard	-
Burst Balloons	hard	-
Longest Increasing Path in a Matrix	hard	-

Problem	Difficulty	Video
Majority Element 1 - with n by 2 definition	easy	-
Jump Game 2 - Get min jumps	medium	-
Jump Game 1 - Check if it reaches last index	medium
Gas Station	medium	-
Valid Parenthesis String	medium	-
Partition Labels	medium	-
Hand of Straights	medium
Merge Triplets to Form Target Triplet	medium	-

Problem	Difficulty	Video
Meeting Rooms 1 - Can person attend all meetings	easy
Merge Overlapping Intervals	medium
Insert Interval	medium
Maximum Intervals Overlap Count	medium
Non-overlapping Intervals	medium

Problem	Difficulty	Video
Single Number 1 - All elements except one occur twice	easy
Reverse Bits	easy
Number of 1 Bits	easy
Missing Number	easy
Counting Bits	easy
Multiply Strings	medium	-
Implement Power Function 1	medium	-
Sum of Two Integers	medium
Detect Squares	medium	-
Maximum Points on a Line	hard	-

Problem	Difficulty	Video
Number of Connected Components in an Undirected Graph	medium	-
Evaluate Division	medium	-
Redundant Connection	medium	-
Accounts Merge	medium	-

Arrays & Hashing