🏆 LeetCode Solutions

A collection of 374 solved LeetCode problems in C++, organized by difficulty. Whether you're preparing for coding interviews or sharpening your problem-solving skills, feel free to explore!

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📊 Progress Overview

Difficulty	Solved	Folder
🟢 Easy	168	Easy Problems
🟡 Medium	177	Medium Problems
🔴 Hard	29	Hard Problems
Total	374

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📚 Table of Contents

• Easy Problems
• Medium Problems
• Hard Problems
• Topics Covered

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🟢 Easy Problems

#	Problem	Solution
1	Two Sum	C++
9	Palindrome Number	C++
13	Roman to Integer	C++
20	Valid Parentheses	C++
21	Merge Two Sorted Lists	C++
26	Remove Duplicates from Sorted Array	C++
27	Remove Element	C++
28	Find the Index of the First Occurrence in a String	C++
35	Search Insert Position	C++
58	Length of Last Word	C++
66	Plus One	C++
67	Add Binary	C++
70	Climbing Stairs	C++
83	Remove Duplicates from Sorted List	C++
94	Binary Tree Inorder Traversal	C++
100	Same Tree	C++
101	Symmetric Tree	C++
104	Maximum Depth of Binary Tree	C++
110	Balanced Binary Tree	C++
111	Minimum Depth of Binary Tree	C++
112	Path Sum	C++
121	Best Time to Buy and Sell Stock	C++
125	Valid Palindrome	C++
136	Single Number	C++
141	Linked List Cycle	C++
144	Binary Tree Preorder Traversal	C++
145	Binary Tree Postorder Traversal	C++
160	Intersection of Two Linked Lists	C++
169	Majority Element	C++
191	Number of 1 Bits	C++
203	Remove Linked List Elements	C++
205	Isomorphic Strings	C++
206	Reverse Linked List	C++
222	Count Complete Tree Nodes	C++
231	Power of Two	C++
234	Palindrome Linked List	C++
242	Valid Anagram	C++
257	Binary Tree Paths	C++
258	Add Digits	C++
268	Missing Number	C++
278	First Bad Version	C++
283	Move Zeroes	C++
326	Power of Three	C++
338	Counting Bits	C++
342	Power of Four	C++
344	Reverse String	C++
345	Reverse Vowels of a String	C++
349	Intersection of Two Arrays	C++
350	Intersection of Two Arrays II	C++
367	Valid Perfect Square	C++
374	Guess Number Higher or Lower	C++
383	Ransom Note	C++
389	Find the Difference	C++
404	Sum of Left Leaves	C++
409	Longest Palindrome	C++
414	Third Maximum Number	C++
455	Assign Cookies	C++
476	Number Complement	C++
507	Perfect Number	C++
509	Fibonacci Number	C++
543	Diameter of Binary Tree	C++
557	Reverse Words in a String III	C++
590	N-ary Tree Postorder Traversal	C++
594	Longest Harmonious Subsequence	C++
628	Maximum Product of Three Numbers	C++
700	Search in a Binary Search Tree	C++
703	Kth Largest Element in a Stream	C++
704	Binary Search	C++
724	Find Pivot Index	C++
744	Find Smallest Letter Greater Than Target	C++
747	Largest Number At Least Twice of Others	C++
766	Toeplitz Matrix	C++
860	Lemonade Change	C++
876	Middle of the Linked List	C++
884	Uncommon Words from Two Sentences	C++
917	Reverse Only Letters	C++
977	Squares of a Sorted Array	C++
1002	Find Common Characters	C++
1047	Remove All Adjacent Duplicates In String	C++
1051	Height Checker	C++
1071	Greatest Common Divisor of Strings	C++
1122	Relative Sort Array	C++
1128	Number of Equivalent Domino Pairs	C++
1137	N-th Tribonacci Number	C++
1207	Unique Number of Occurrences	C++
1287	Element Appearing More Than 25% In Sorted Array	C++
1290	Convert Binary Number in a Linked List to Integer	C++
1323	Maximum 69 Number	C++
1351	Count Negative Numbers in a Sorted Matrix	C++
1380	Lucky Numbers in a Matrix	C++
1394	Find Lucky Integer in an Array	C++
1422	Maximum Score After Splitting a String	C++
1431	Kids With the Greatest Number of Candies	C++
1460	Make Two Arrays Equal by Reversing Subarrays	C++
1464	Maximum Product of Two Elements in an Array	C++
1480	Running Sum of 1d Array	C++
1512	Number of Good Pairs	C++
1518	Water Bottles	C++
1528	Shuffle String	C++
1544	Make The String Great	C++
1550	Three Consecutive Odds	C++
1572	Matrix Diagonal Sum	C++
1598	Crawler Log Folder	C++
1608	Special Array With X Elements Greater Than or Equal X	C++
1614	Maximum Nesting Depth of the Parentheses	C++
1624	Largest Substring Between Two Equal Characters	C++
1636	Sort Array by Increasing Frequency	C++
1662	Check If Two String Arrays are Equivalent	C++
1684	Count the Number of Consistent Strings	C++
1688	Count of Matches in Tournament	C++
1700	Number of Students Unable to Eat Lunch	C++
1704	Determine if String Halves Are Alike	C++
1716	Calculate Money in Leetcode Bank	C++
1732	Find the Highest Altitude	C++
1748	Sum of Unique Elements	C++
1752	Check if Array Is Sorted and Rotated	C++
1768	Merge Strings Alternately	C++
1791	Find Center of Star Graph	C++
1832	Check if the Sentence Is Pangram	C++
1863	Sum of All Subset XOR Totals	C++
1894	Find the Student that Will Replace the Chalk	C++
1920	Build Array from Permutation	C++
1945	Sum of Digits of String After Convert	C++
1957	Delete Characters to Make Fancy String	C++
1979	Find Greatest Common Divisor of Array	C++
2000	Reverse Prefix of Word	C++
2022	Convert 1D Array Into 2D Array	C++
2037	Minimum Number of Moves to Seat Everyone	C++
2053	Kth Distinct String in an Array	C++
2073	Time Needed to Buy Tickets	C++
2094	Finding 3-Digit Even Numbers	C++
2108	Find First Palindromic String in the Array	C++
2124	Check if All A's Appears Before All B's	C++
2210	Count Hills and Valleys in an Array	C++
2215	Find the Difference of Two Arrays	C++
2220	Minimum Bit Flips to Convert Number	C++
2248	Intersection of Multiple Arrays	C++
2264	Largest 3-Same-Digit Number in String	C++
2331	Evaluate Boolean Binary Tree	C++
2418	Sort the People	C++
2441	Largest Positive Integer That Exists With Its Negative	C++
2485	Find the Pivot Integer	C++
2540	Minimum Common Value	C++
2582	Pass the Pillow	C++
2678	Number of Senior Citizens	C++
2706	Buy Two Chocolates	C++
2778	Sum of Squares of Special Elements	C++
2839	Check if Strings Can be Made Equal With Operations I	C++
2946	Matrix Similarity After Cyclic Shifts	C++
2980	Check if Bitwise OR Has Trailing Zeros	C++
3005	Count Elements With Maximum Frequency	C++
3110	Score of a String	C++
3136	Valid Word	C++
3162	Find the Number of Good Pairs I	C++
3184	Count Pairs That Form a Complete Day I	C++
3190	Find Minimum Operations to Make All Elements Divisible by Three	C++
3194	Minimum Average of Smallest and Largest Elements	C++
3304	Find the K-th Character in String Game I	C++
3330	Find the Original Typed String I	C++
3487	Maximum Unique Subarray Sum After Deletion	C++

📄 Bonus Easy Problems (unnumbered)

Problem	Solution
Complement of Base 10	C++
Number of 1 Bits	C++
Number Complement	C++
Pascal's Triangle	C++
Pascal's Triangle II	C++
Sqrt Number (without built-in)	C++
Subtract Product and Sum of Digits	C++
Subarray Sum Equals Target	C++

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🟡 Medium Problems

#	Problem	Solution
2	Add Two Numbers	C++
8	String to Integer (atoi)	C++
16	3Sum Closest	C++
24	Swap Nodes in Pairs	C++
33	Search in Rotated Sorted Array	C++
34	Find First and Last Position of Element in Sorted Array	C++
40	Combination Sum II	C++
53	Maximum Subarray	C++
54	Spiral Matrix	C++
59	Spiral Matrix II	C++
61	Rotate List	C++
74	Search a 2D Matrix	C++
78	Subsets	C++
81	Search in Rotated Sorted Array II	C++
88	Merge Sorted Array	C++
90	Subsets II	C++
98	Validate Binary Search Tree	C++
102	Binary Tree Level Order Traversal	C++
103	Binary Tree Zigzag Level Order Traversal	C++
105	Construct Binary Tree from Preorder and Inorder Traversal	C++
106	Construct Binary Tree from Inorder and Postorder Traversal	C++
107	Binary Tree Level Order Traversal II	C++
113	Path Sum II	C++
129	Sum Root to Leaf Numbers	C++
137	Single Number II	C++
142	Linked List Cycle II	C++
147	Insertion Sort List	C++
148	Sort List	C++
153	Find Minimum in Rotated Sorted Array	C++
162	Find Peak Element	C++
164	Maximum Gap	C++
165	Compare Version Numbers	C++
167	Two Sum II	C++
172	Factorial Trailing Zeroes	C++
179	Largest Number	C++
199	Binary Tree Right Side View	C++
201	Bitwise AND of Numbers Range	C++
204	Count Primes	C++
215	Kth Largest Element in an Array	C++
219	Contains Duplicate II	C++
229	Majority Element II	C++
230	Kth Smallest Element in a BST	C++
235	Lowest Common Ancestor of a BST	C++
236	Lowest Common Ancestor of a Binary Tree	C++
237	Delete Node in a Linked List	C++
238	Product of Array Except Self	C++
240	Search a 2D Matrix II	C++
241	Different Ways to Add Parentheses	C++
260	Single Number III	C++
264	Ugly Number II	C++
287	Find the Duplicate Number	C++
328	Odd Even Linked List	C++
334	Increasing Triplet Subsequence	C++
371	Sum of Two Integers	C++
378	Kth Smallest Element in a Sorted Matrix	C++
421	Maximum XOR of Two Numbers in an Array	C++
437	Path Sum III	C++
442	Find All Duplicates in an Array	C++
443	String Compression	C++
445	Add Two Numbers II	C++
449	Serialize and Deserialize BST	C++
515	Find Largest Value in Each Tree Row	C++
523	Continuous Subarray Sum	C++
539	Minimum Time Difference	C++
592	Fraction Addition and Subtraction	C++
624	Maximum Distance in Arrays	C++
633	Sum of Square Numbers	C++
637	Average of Levels in Binary Tree	C++
648	Replace Words	C++
650	2 Keys Keyboard	C++
678	Valid Parenthesis String	C++
725	Split Linked List in Parts	C++
790	Domino and Tromino Tiling	C++
791	Custom Sort String	C++
826	Most Profit Assigning Work	C++
837	New 21 Game	C++
838	Push Dominoes	C++
840	Magic Squares In Grid	C++
846	Hand of Straights	C++
852	Peak Index in a Mountain Array	C++
874	Walking Robot Simulation	C++
880	Decoded String at Index	C++
881	Boats to Save People	C++
885	Spiral Matrix III	C++
898	Bitwise ORs of Subarrays	C++
912	Sort an Array	C++
945	Minimum Increment to Make Array Unique	C++
947	Most Stones Removed with Same Row or Column	C++
959	Regions Cut By Slashes	C++
974	Subarray Sums Divisible by K	C++
988	Smallest String Starting From Leaf	C++
1007	Minimum Domino Rotations For Equal Row	C++
1008	Construct BST from Preorder Traversal	C++
1038	BST to Greater Sum Tree	C++
1052	Grumpy Bookstore Owner	C++
1105	Filling Bookcase Shelves	C++
1110	Delete Nodes And Return Forest	C++
1140	Stone Game II	C++
1190	Reverse Substrings Between Each Pair of Parentheses	C++
1208	Get Equal Substrings Within Budget	C++
1233	Remove Sub-Folders from the Filesystem	C++
1248	Count Number of Nice Subarrays	C++
1249	Minimum Remove to Make Valid Parentheses	C++
1296	Divide Array in Sets of K Consecutive Numbers	C++
1310	XOR Queries of a Subarray	C++
1325	Delete Leaves With a Given Value	C++
1334	Find the City With the Smallest Number of Neighbors	C++
1347	Minimum Number of Steps to Make Two Strings Anagram	C++
1367	Linked List in Binary Tree	C++
1371	Find the Longest Substring Containing Vowels in Even Counts	C++
1382	Balance a Binary Search Tree	C++
1395	Count Number of Teams	C++
1438	Longest Continuous Subarray With Absolute Diff ≤ Limit	C++
1482	Minimum Number of Days to Make m Bouquets	C++
1498	Number of Subsequences That Satisfy the Given Sum Condition	C++
1508	Range Sum of Sorted Subarray Sums	C++
1509	Minimum Difference Between Largest and Smallest Value in Three Moves	C++
1514	Path with Maximum Probability	C++
1530	Number of Good Leaf Nodes Pairs	C++
1552	Magnetic Force Between Two Balls	C++
1605	Find Valid Matrix Given Row and Column Sums	C++
1657	Determine if Two Strings Are Close	C++
1679	Max Number of K-Sum Pairs	C++
1685	Sum of Absolute Differences in a Sorted Array	C++
1695	Maximum Erasure Value	C++
1701	Average Waiting Time	C++
1717	Maximum Score From Removing Substrings	C++
1823	Find the Winner of the Circular Game	C++
1905	Count Sub Islands	C++
1910	Remove All Occurrences of a Substring	C++
1937	Maximum Number of Points with Cost	C++
1948	Delete Duplicate Folders in System	C++
2028	Find Missing Observations	C++
2044	Count Number of Maximum Bitwise-OR Subsets	C++
2058	Find the Min and Max Number of Nodes Between Critical Points	C++
2096	Step-By-Step Directions From a Binary Tree Node to Another	C++
2125	Number of Laser Beams in a Bank	C++
2134	Minimum Swaps to Group All 1's Together II	C++
2181	Merge Nodes in Between Zeros	C++
2192	All Ancestors of a Node in a DAG	C++
2196	Create Binary Tree From Descriptions	C++
2285	Maximum Total Importance of Roads	C++
2326	Spiral Matrix IV	C++
2348	Number of Zero-Filled Subarrays	C++
2390	Removing Stars From a String	C++
2402	Meeting Rooms III	C++
2410	Maximum Matching of Players With Trainers	C++
2411	Smallest Subarrays With Maximum Bitwise OR	C++
2419	Longest Subarray With Maximum Bitwise AND	C++
2486	Append Characters to String to Make Subsequence	C++
2487	Remove Nodes From Linked List	C++
2807	Insert Greatest Common Divisors in Linked List	C++
2816	Double a Number Represented as a Linked List	C++
2870	Minimum Number of Operations to Make Array Empty	C++
2918	Minimum Equal Sum of Two Arrays After Replacing Zeros	C++
2976	Minimum Cost to Convert String I	C++
3016	Minimum Number of Pushes to Type Word II	C++
3075	Maximize Happiness of Selected Children	C++
3164	Find the Number of Good Pairs II	C++
3185	Count Pairs That Form a Complete Day II	C++
3191	Minimum Operations to Make Binary Array Elements Equal to One I	C++
3201	Find the Maximum Length of Valid Subsequence I	C++
3202	Find the Maximum Length of Valid Subsequence II	C++
3217	Delete Nodes From Linked List Present in Array	C++
3341	Find Minimum Time to Reach Last Room I	C++
3342	Find Minimum Time to Reach Last Room II	C++
3439	Reschedule Meetings for Maximum Free Time I	C++
3440	Reschedule Meetings for Maximum Free Time II	C++
3546	Equal Sum Grid Partition I	C++

📄 Bonus Medium Problems (unnumbered)

Problem	Solution
3Sum	C++
Delete Kth Node from End	C++
Distinct Array & Target Integer Combinations	C++
Find All Duplicates in an Array	C++
Reverse a Number	C++
Rotate Array	C++
Sort Colors (Dutch National Flag)	C++

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🔴 Hard Problems

#	Problem	Solution
23	Merge k Sorted Lists	C++
154	Find Minimum in Rotated Sorted Array II	C++
220	Contains Duplicate III	C++
273	Integer to English Words	C++
330	Patching Array	C++
502	IPO	C++
564	Find the Closest Palindrome	C++
664	Strange Printer	C++
679	24 Game	C++
719	Find K-th Smallest Pair Distance	C++
726	Number of Atoms	C++
995	Minimum Number of K Consecutive Bit Flips	C++
1568	Minimum Number of Days to Disconnect Island	C++
1579	Remove Max Number of Edges to Keep Graph Fully Traversable	C++
1900	The Earliest and Latest Rounds Where Players Compete	C++
2045	Second Minimum Time to Reach Destination	C++
2071	Maximum Number of Tasks You Can Assign	C++
2163	Minimum Difference in Sums After Removal of Elements	C++
2322	Minimum Score After Removals on a Tree	C++
2392	Build a Matrix With Conditions	C++
2699	Modify Graph Edge Weights	C++
2751	Robot Collisions	C++
3307	Find the K-th Character in String Game II	C++
3333	Find the Original Typed String II	C++
3343	Count Number of Balanced Permutations	C++
3363	Find the Maximum Number of Fruits Collected	C++
3480	Maximize Subarrays After Removing One Conflicting Pair	C++

📄 Bonus Hard Problems (unnumbered)

Problem	Solution
Median of Two Sorted Arrays	C++
Reverse Nodes in k-Group	C++

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🗂 Topics Covered

Topic	Example Problems
Arrays & Hashing	Two Sum, Product of Array Except Self, Majority Element
Two Pointers	3Sum Closest, Two Sum II, Move Zeroes, Boats to Save People
Sliding Window	Grumpy Bookstore Owner, Get Equal Substrings Within Budget
Binary Search	Search in Rotated Sorted Array, Find Peak Element, Binary Search
Linked Lists	Merge k Sorted Lists, Reverse Linked List, Linked List Cycle
Trees	Maximum Depth of Binary Tree, Path Sum, LCA, Serialize BST
Stacks	Valid Parentheses, Remove All Adjacent Duplicates
Sorting	Sort an Array, Sort List, Insertion Sort List
Bit Manipulation	Single Number, Counting Bits, XOR Queries
Dynamic Programming	Climbing Stairs, Fibonacci, Stone Game II, Domino Tiling
Greedy	Assign Cookies, Lemonade Change, IPO, Patching Array
Graphs	Path with Maximum Probability, Regions Cut By Slashes
Matrix	Spiral Matrix, Search a 2D Matrix, Toeplitz Matrix
Math	Factorial Trailing Zeroes, Power of Two/Three/Four
Strings	String Compression, Valid Anagram, Merge Strings Alternately

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🚀 How to Use

1. Clone the repo

   git clone <repo-url>
   cd LeetCode-Problems

2. Compile any solution

   g++ -std=c++17 -o solution "Easy Problems/1_Two-sum.cpp"
   ./solution

3. Browse by difficulty — use the tables above or navigate the folders directly.

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🤝 Contributing

Found a better approach? Want to add a new solution? PRs are welcome!

1. Fork the repository
2. Add your solution in the appropriate difficulty folder
3. Follow the naming convention: <number>_<Problem_Name>.cpp
4. Submit a pull request

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