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This Challenge is beginner-friendly and available to both Premium and non-Premium users. It consists of 30-31 daily problems depends on the month type. A problem is added here each day, and you have 24 hours to make a valid submission for it in order to be eligible for rewards.

In this LeetCode Challenge, we challenge participants with a problem from our carefully curated collection of interview problems every 24 hours. All users with all levels of coding background are welcome to join!

📌 When is August's LeetCoding Challenge?Start: August 1st, 12:00 AM in Pacific Time (UTC-7)

End: August 31th, 23:59 PM in Pacific Time (UTC-7)

🚩 How do I join August's LeetCoding Challenge?

To join, just start solving problems in August's LeetCoding Challenge Explore Card. No registration is required. The first problem will appear in the Explore card on August's 1st, 12 a.m. Pacific Time and you will have 24 hours to solve that challenge. A problem is added in the Explore card each day. For more details such as the Challenge Rules, please refer to the Explore card.

🎁 Rewards:

Completing each daily challenge. (+10 LeetCoins)

Completing 25 to 30 daily challenges will be eligible for an additional 100 LeetCoins. (Total = 350 to 400 LeetCoins)

Completing all 31 daily challenges will be eligible for 2X the reward, plus a chance to win a secret prize ( Total = 620 LeetCoins + *Lucky Draw)!

Lucky Draw: Those who complete all 31 daily challenges will be automatically entered into a Lucky Draw, where LeetCode staff will randomly select 3 lucky participants to each receive one LeetCode Cap on top of their rewards!

🤩 What are you waiting for? Mark your calendar now to start the August LeetCoding Challenge on August 1st, 2022!

#	Title	Solution	Tags	Youtube
1	Backspace String Compare		two pointersstringstacksimulation
2	Sort Array By Parity		arraytwo pointersstring
3	Shortest Unsorted Continuous Subarray		arraytwo pointersstackgreedysortingmonotonic stack
4	Max Number of K-Sum Pairs		arrayhash tabletwo pointerssorting
5	Implement Stack using Queues		stackdesignqueue
6	Remove All Adjacent Duplicates in String II		stringstack
7	132 Pattern		arraybinary searchstackmonotonic stackordered set
8	Flatten Nested List Iterator		stacktreedepth-first searchdesignqueueiterator
9	Letter Combinations of a Phone Number		hash tablestringbacktracking
10	Combination Sum III		arraybacktracking
11	Count Sorted Vowel Strings		dynamic programming
12	Permutations II		arraybacktracking
13	Populating Next Right Pointers in Each Node II		linked listtreedepth-first searchbreadth-first searchbinary tree
14	Network Delay Time		depth-first searchbreadth-first searchgraphheap(priority queue)shortest path
15	Deepest Leaves Sum		treedepth-first searchbreadth-first searchbinary tree
16	Shortest Path in Binary Matrix		arraybreadth-first searchmatrix
17	Find a Corresponding Node of a Binary Tree in a Clone of That Tree		treedepth-first searchbreadth-first searchbinary tree
18	Critical Connections in a Network		depth-first searchgraphbiconnected component
19	Longest Increasing Path in a Matrix		dynamic programmingdepth-first searchbreadth-first searchgraphtopological sortmemorization
20	Unique Paths II		arraydynamic programmingmatrix
21	Coin Change		arraydynamic programmingbreadth-first search
22	Palindromic Substrings		stringdynamic programming
23	Ones and Zeroes		arraystringdynamic programming
24	Longest Valid Parentheses		stringdynamic programmingstack
25	Russian Doll Envelopes		arraybinary searchdynamic programmingsorting
26	Number of 1 Bits		divide and conquerbit manipulation
27	Number of Steps to Reduce a Number to Zero		mathbit manipulation
28	Missing Number		arrayhash tablemathbinary searchbit manipulationsorting
29	Maximum Product of Word Lengths		arraystringbit manipulation
30	Divide Two Integers		mathbit manipulation
31	Check If a String Contains All Binary Codes of Size K		hash tablestringbit manipulationrolling hashhash function

#	Title	Solution	Tags	Youtube
1	Running Sum of 1D Array		arrayprefix sum
2	Transpose Matrix		arraymatrixsimulation
3	Range Sum Query 2D - Immutable		array
4	N-Queens		arraybacktracking
5	N-Queens-II		backtracking
6	Intersection of Two Linked Lists		hash tablelinked listtwo pointers
7	Merge Sorted Array		arraytwo pointerssorting
8	Remove Palindromic Subsequences		two pointersstring
9	Two Sum II - Input Array Is Sorted		arraytwo pointersbinary search
10	Longest Substring Without Repeating Characters		hash tablestringsliding window
11	Minimum Operations to Reduce X to Zero		arrayhash tablebinary searchsliding windowprefix sum
12	Maximum Erasure Value		arrayhash tablesliding window
13	Triangle		arraydynamic programming
14	Delete Operation for Two Strings		stringdynamic programming
15	Longest String Chain		arrayhash tabletwo pointersstringdynamic programming
16	Longest Palindromic Substring		stringdynamic programming
17	Binary Tree Cameras		dynamic programmingtreedepth-first searchbinary tree
18	Prefix and Suffix Search		stringdesigntrie
19	Search Suggestions System		arraystringtrie
20	Short Encoding of Words		arrayhash tablestringtrie
21	Furthest Building You Can Reach		arraygreedyheap(priority queue)
22	Kth Largest Element in an Array		arraydivide and conquersortingheap(priority queue)quickselect
23	Course Schedule III		arraygreedyheap(priority queue)
24	Construct Target Array With Multiple Sums		arrayheap(priority queue)
25	Non-decreasing Array		array
26	Maximum Points You Can Obtain from Cards		arraysliding windowprefix sum
27	Partitioning Into Minimum Number Of Deci-Binary Numbers		stringgreedy
28	Minimum Deletions to Make Character Frequencies Unique		stringgreedysorting
29	Queue Reconstruction by Height		arraygreedybinary indexed treesegment treesorting
30	Minimum Moves to Equal Array Elements II		string

#	Title	Solution	Tags	Youtube
1	Maximum Units on a Truck		arraygreedysorting
2	Maximum Area of a Piece of Cake After Horizontal and Vertical Cuts		arraygreedysorting
3	Wiggle Subsequence		arraydynamic programminggreedy
4	Candy		arraygreedy
5	Longest Consecutive Sequence		arrayhash tableunion find
6	Fibonacci Number		mathdynamic programmingrecursionmemoization
7	Interleaving String		stringdynamic programming
8	Paint House III		arraydynamic programming
9	Jump Game VI		arraydynamic programmingqueuesliding windowheap(priority queue)monotonic queue
10	Min Cost Climbing Stairs		arraydynamic programming
11	Binary Tree Right Side View		treesdepth-first searchbreadth-first searchbinary tree
12	Matchsticks to Square		arraydynamic programmingbacktrackingbit manipulationbitmask
13	Binary Tree Level Order Traversal		treebreadth-first searchbinary tree
14	Construct Binary Tree from Preorder and Inorder Traversal		arrayhash tabledivide and conquertreebinary tree
15	Max Area of Island		arraydepth-first searchbreadth-first searchunion findmatrix
16	Out of Boundary Paths		dynamic programming
17	K Inverse Pairs Array		dynamic programming
18	Number of Submatrices That Sum to Target		arrayhash tablematrixprefix sum
19	Pascal's Triangle		arraydynamic programming
20	Number of Matching Subsequences		hash tablestringtriesorting
21	Reverse Linked List II		Linked List
22	Partition List		Linked ListTwo Pointers
23	Count of Smaller Numbers After Self		arraybinary searchdivide and conquerbinary indexed treesegment treemerge sortordered set
24	Search a 2D Matrix II		arraybinary searchdivide and conquermatrix
25	Find First and Last Position of Element in Sorted Array		arraybinary search
26	Lowest Common Ancestor of a Binary Tree		treedepth-first searchbinary tree
27	Flatten Binary Tree to Linked List		linked liststacktreedepth-first searchbinary tree
28	Valid Anagram		hash tablestringsorting
29	Find and Replace Pattern		arrayhash tablestring
30	Word Subsets		arrayhash tablestring
31	Range Sum Query - Mutable		arraydesignbinary indexed treesegment tree

#	Title	Solution	Tags	Youtube
1	Unique Paths		mathdynamic programmingcombinatorics
2	Kth Smallest Element in a Sorted Matrix		arraybinary searchsortingheap(priority queue)matrix
3	My Calendar I		binary searchdesignsegment treeordered set
4	Mirror Reflection		mathgeometry
5	Combination Sum IV		arraydynamic programming
6	Poor Pigs		mathdynamic programmingcombinatorics
7	Count Vowels Permutation		dynamic programming
8	Longest Increasing Subsequence		arraybinary searchdynamic programming
9	Binary Trees With Factors		arrayhash tabledynamic programming
10	Convert Sorted Array to Binary Search Tree		arraydivide and conquertreebinary search treebinary search
11	Validate Binary Search Tree		treedepth-first searchbinary search treebianry tree
12	Lowest Common Ancestor of a Binary Search Tree		treedepth-first searchbinary search treebianry tree
13	Substring with Concatenation of All Words		hash tablestringsliding window
14	Word Ladder II		hash tablestringbacktrackingbreadth-first search
15	Roman to Integer		hash tablemathstring
16	First Unique Character in a String		hash tablestringqueuecounting
17	Unique Morse Code Words		arrayhash tablestring
18	Reduce Array Size to The Half		arrayhash tablegreedysortingheap(priority queue)
19	Split Array into Consecutive Subsequences		arrayhash tablegreedyheap(priority queue)
20	Minimum Number of Refueling Stops		arraydynamic programminggreedyheap(priority queue)
21	Stamping The Sequence		stringstackgreedyqueue
22	Power of Four		mathbit manipulationrecursion
23	Palindrome Linked List		linked listtwo pointersstackrecursion
24	Power of Three		mathrecursion
25	Ransom Note		hash tablestringcounting
26	Reordered Power of 2		mathstringcountingenumeration
27	Max Sum of Rectangle No Larger Than K		arraybinary searchmatrixprefix sumordered set
28	Sort the Matrix Diagonally		arraysortingmatrix
29	Number of Islands		arraydepth-first searchbreadth-first searchunion findmatrix
30	Rotate Image		arraymathmatrix
31	Pacific Atlantic Water Flow		arraydepth-first searchbreadth-first searchmatrix