Competitive Programming Solutions

A collection of solved competitive programming problems across multiple online judges.

📊 Stats

Platform	Count
LeetCode	275 problems
UVA Online Judge	245 solutions
LightOJ	171 solutions
Codeforces	212 contests + 1 gym
TopCoder	55 problems
SPOJ	20 solutions
Total	979+

🔗 Online Judge Profiles

• UVA Online Judge → the_redback
• LightOJ → 5399
• Codeforces → the_redback
• TopCoder → the_redback
• CodeChef → the_redback
• HackerRank → the_redback
• SPOJ → maruf2hin

📑 Table of Contents

• LeetCode
  • Array & Hashing
  • Two Pointers
  • Sliding Window
  • Stack & Queue
  • Binary Search
  • Linked List
  • Tree
  • Graph
  • Backtracking
  • Dynamic Programming
  • Greedy
  • Intervals
  • String
  • Bit Manipulation
  • Math & Geometry
  • Design
  • Concurrency
  • JavaScript
• UVA Online Judge
  • Graph
  • Dynamic Programming
  • Math & Number Theory
  • Greedy
  • Backtracking
  • Geometry
  • Sorting & Searching
  • Simulation & Ad Hoc
• LightOJ
  • Graph
  • Dynamic Programming
  • Math & Number Theory
  • Data Structures
  • Backtracking
  • String
  • Sorting & Searching
  • Simulation & Ad Hoc
• Codeforces
  • Dynamic Programming
  • Graph
  • Math & Number Theory
  • Data Structures
  • Greedy
  • Sorting & Searching
• SPOJ
  • Data Structures
  • Dynamic Programming
  • Graph
  • Math & Number Theory
  • Greedy
  • Sorting & Searching
  • Simulation & Ad Hoc
• TopCoder
  • Dynamic Programming
  • Greedy
  • String
  • Math & Geometry
  • Simulation & Ad Hoc

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🟡 LeetCode

Array & Hashing

#	Problem
1	1. Two Sum
26	26. Remove Duplicates from Sorted Array
27	27. Remove Element
36	36. Valid Sudoku
48	48. Rotate Image
49	49. Group Anagrams
53	53. Maximum Subarray
54	54. Spiral Matrix
58	58. Length of Last Word
59	59. Spiral Matrix II
66	66. Plus One
73	73. Set Matrix Zeroes
80	80. Remove Duplicates from Sorted Array II
88	88. Merge Sorted Array
118	118. Pascals Triangle
128	128. Longest Consecutive Sequence
136	136. Single Number
169	169. Majority Element
189	189. Rotate Array
205	205. Isomorphic Strings
217	217. Contains Duplicate
219	219. Contains Duplicate II
238	238. Product of Array Except Self
242	242. Valid Anagram
268	268. Missing Number
271	271. Encode and Decode Strings
274	274. H Index
283	283. Move Zeroes
289	289. Game of Life
290	290. Word Pattern
299	299. Bulls and Cows
347	347. Top K Frequent Elements
350	350. Intersection of Two Arrays II
383	383. Ransom Note
387	387. First Unique Character in a String
412	412. Fizz Buzz
448	448. Find All Numbers Disappeared in an Array
523	523. Continuous Subarray Sum
560	560. Subarray Sum Equals K
782	782. Jewels and Stones
965	965. Unique Email Addresses
1112	1112. Find Words That Can Be Formed By Characters
1580	1580. Shuffle the Array
2058	2058. Concatenation of Array
3251	3251. Maximum Area of Longest Diagonal Rectangle

Two Pointers

#	Problem
11	11. Container with Most Water
15	15. 3Sum
16	16. 3Sum Closest
125	125. Valid Palindrome
167	167. Two Sum II Input Array is Sorted
259	259. 3Sum Smaller
344	344. Reverse String
392	392. Is Subsequence

Sliding Window

#	Problem
3	3. Longest Substring Without Repeating Characters
30	30. Substring with Concatenation of All Words
76	76. Minimum Window Substring
159	159. Longest Substring with At Most Two Distinct Characters
209	209. Minimum Size Subarray Sum
239	239. Sliding Window Maximum
424	424. Longest Repeating Character Replacement
480	480. Sliding Window Median
485	485. Max Consecutive Ones
539	539. Minimum Time Difference
940	940. Fruit Into Baskets
1034	1034. Subarrays with K Different Integers
1046	1046. Max Consecutive Ones III
1370	1370. Count Number of Nice Subarrays

Stack & Queue

#	Problem
20	20. Valid Parentheses
71	71. Simplify Path
150	150. Evaluate Reverse Polish Notation
155	155. Min Stack
394	394. Decode String
503	503. Next Greater Element II
678	678. Valid Parenthesis String
860	860. Design Circular Queue
874	874. Backspace String Compare
943	943. Sum of Subarray Minimums
2227	2227. Sum of Subarray Ranges

Binary Search

#	Problem
4	4. Median of Two Sorted Arrays
33	33. Search in Rotated Sorted Array
34	34. Find First and Last Position of Element in Sorted Array
153	153. Find Minimum in Rotated Sorted Array
154	154. Find Minimum in Rotated Sorted Array II
278	278. First Bad Version
410	410. Split Array Largest Sum
668	668. Kth Smallest Number in Multiplication Table
882	882. Peak Index in a Mountain Array

Linked List

#	Problem
2	2. Add Two Numbers
19	19. Remove Nth Node from End of List
21	21. Merge Two Sorted Lists
23	23. Merge K Sorted Lists
25	25. Reverse Nodes in k-Group
138	138. Copy List with Random Pointer
141	141. Linked List Cycle
143	143. Reorder List
160	160. Intersection of Two Linked Lists
206	206. Reverse Linked List
234	234. Palindrome Linked List
237	237. Delete Node in a Linked List
445	445. Add Two Numbers II
908	908. Middle of the Linked List

Tree

#	Problem
94	94. Binary Tree Inorder Traversal
98	98. Validate Binary Search Tree
100	100. Same Tree
101	101. Symmetric Tree
102	102. Binary Tree Level Order Traversal
103	103. Binary Tree Zigzag Level Order Traversal
104	104. Maximum Depth of Binary Tree
105	105. Construct Binary Tree from Preorder and Inorder Traversal
106	106. Construct Binary Tree from Inorder and Postorder Traversal
108	108. Convert Sorted Array to Binary Search Tree
116	116. Populating Next Right Pointers in Each Node
117	117. Populating Next Right Pointers in Each Node II
124	124. Binary Tree Maximum Path Sum
222	222. Count Complete Tree Nodes
226	226. Invert Binary Tree
230	230. Kth Smallest Element in a BST
235	235. Lowest Common Ancestor of a Binary Search Tree
236	236. Lowest Common Ancestor of a Binary Tree
297	297. Serialize and Deserialize Binary Tree
366	366. Find Leaves of Binary Tree
449	449. Serialize and Deserialize BST
450	450. Delete Node in a BST
543	543. Diameter of Binary Tree
572	572. Subtree of Another Tree
784	784. Insert Into a Binary Search Tree
988	988. Flip Equivalent Binary Trees
2217	2217. Step By Step Directions from a Binary Tree Node to Another

Graph

#	Problem
127	127. Word Ladder
133	133. Clone Graph
200	200. Number of Islands
207	207. Course Schedule
210	210. Course Schedule II
261	261. Graph Valid Tree
269	269. Alien Dictionary
323	323. Number of Connected Components in an Undirected Graph
399	399. Evaluate Division
417	417. Pacific Atlantic Water Flow
505	505. The Maze II
675	675. Cut Off Trees For Golf Event
733	733. Flood Fill
984	984. Most Stones Removed with Same Row or Column
989	989. Largest Component Size By Common Factor
1036	1036. Rotting Oranges
1414	1414. Shortest Path in a Grid with Obstacles Elimination
2220	2220. Find All Possible Recipes from Given Supplies
2409	2409. Number of Increasing Paths in a Grid

Backtracking

#	Problem
17	17. Letter Combinations of a Phone Number
22	22. Generate Parentheses
31	31. Next Permutation
39	39. Combination Sum
40	40. Combination Sum II
46	46. Permutations
47	47. Permutations II
77	77. Combinations
78	78. Subsets
79	79. Word Search
90	90. Subsets II
131	131. Palindrome Partitioning
212	212. Word Search II
216	216. Combination Sum III
247	247. Strobogrammatic Number II
351	351. Android Unlock Patterns
425	425. Word Squares
681	681. Next Closest Time
754	754. Cracking the Safe
865	865. Robot Room Cleaner

Dynamic Programming

#	Problem
10	10. Regular Expression Matching
42	42. Trapping Rain Water
44	44. Wildcard Matching
45	45. Jump Game II
55	55. Jump Game
62	62. Unique Paths
70	70. Climbing Stairs
91	91. Decode Ways
121	121. Best Time to Buy and Sell Stock
122	122. Best Time to Buy and Sell Stock II
139	139. Word Break
152	152. Maximum Product Subarray
198	198. House Robber
213	213. House Robber II
300	300. Longest Increasing Subsequence
322	322. Coin Change
329	329. Longest Increasing Path in a Matrix
516	516. Longest Palindromic Subsequence
552	552. Student Attendance Record II
836	836. Race Car
855	855. Count Unique Characters of All Substrings of a Given String
962	962. Flip String to Monotone Increasing
1017	1017. Odd Even Jump
1042	1042. Minimum Cost to Merge Stones
1129	1129. Longest String Chain
1178	1178. Valid Palindrome III
1250	1250. Longest Common Subsequence
1263	1263. Number of Dice Rolls with Target Sum
1437	1437. Minimum Insertion Steps to Make a String Palindrome
1633	1633. Minimum Number of Increments On Subarrays to Form a Target Array
2067	2067. Maximum Number of Points with Cost
2360	2360. Substring with Largest Variance

Greedy

#	Problem
134	134. Gas Station
135	135. Candy
435	435. Non Overlapping Intervals
452	452. Minimum Number of Arrows to Burst Balloons
621	621. Task Scheduler
768	768. Partition Labels
1304	1304. Longest Happy String

Intervals

#	Problem
56	56. Merge Intervals
57	57. Insert Interval
163	163. Missing Ranges
228	228. Summary Ranges
252	252. Meeting Rooms
253	253. Meeting Rooms II

String

#	Problem
5	5. Longest Palindromic Substring
6	6. Zigzag Conversion
7	7. Reverse Integer
8	8. String to Integer atoi
12	12. Integer to Roman
13	13. Roman to Integer
14	14. Longest Common Prefix
28	28. Find the Index of the First Occurrence in a String
43	43. Multiply Strings
68	68. Text Justification
151	151. Reverse Words in a String
165	165. Compare Version Numbers
166	166. Fraction to Recurring Decimal
186	186. Reverse Words in a String II
246	246. Strobogrammatic Number
273	273. Integer to English Words
482	482. License Key Formatting
647	647. Palindromic Substrings
793	793. Swap Adjacent in LR String
827	827. Expressive Words
837	837. Most Common Word
862	862. Find and Replace in String
974	974. Reorder Data in Log Files

Bit Manipulation

#	Problem
190	190. Reverse Bits
191	191. Number of 1 Bits
326	326. Power of Three
338	338. Counting Bits
371	371. Sum of Two Integers
461	461. Hamming Distance

Math & Geometry

#	Problem
202	202. Happy Number
204	204. Count Primes
976	976. Minimum Area Rectangle
2268	2268. Remove All Ones with Row and Column Flips

Design

#	Problem
146	146. LRU Cache
158	158. Read N Characters Given Read4 II Call Multiple Times
208	208. Implement Trie Prefix Tree
211	211. Design Add and Search Words Data Structure
215	215. Kth Largest Element in an Array
295	295. Find Median from Data Stream
303	303. Range Sum Query Immutable
304	304. Range Sum Query 2D Immutable
307	307. Range Sum Query Mutable
308	308. Range Sum Query 2D Mutable
315	315. Count of Smaller Numbers After Self
348	348. Design Tic-Tac-Toe
359	359. Logger Rate Limiter
380	380. Insert Delete GetRandom O(1)
384	384. Shuffle an Array
642	642. Design Search Autocomplete System
731	731. My Calendar II
873	873. Guess the Word
887	887. Minimum Cost to Hire K Workers
879	879. Maximize Distance to Closest Person
931	931. Maximum Frequency Stack
1014	1014. K Closest Points to Origin
1249	1249. Snapshot Array
2139	2139. Detect Squares
2161	2161. Stock Price Fluctuation
2200	2200. Stamping the Grid

Concurrency

#	Problem
1187	1187. Print FooBar Alternately
1203	1203. Print in Order
1209	1209. Design Bounded Blocking Queue

JavaScript

#	Problem
2809	2809. Create Hello World Function

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🔵 UVA Online Judge

245 solutions in C++.

Graph

200, 247, 294, 336, 383, 406, 524, 532, 583-2, 627, 686, 924, 1148, 1148-1, 1160, 1174, 1234, 10004, 10009, 10009-2, 10034, 10042, 10147, 10200, 10305, 10369, 10397, 10397-2, 10462, 10490, 10592, 10653, 10699, 10789, 11060, 11094, 11504, 11631, 11686, 11709, 11730, 11770, 11838, 11960

Dynamic Programming

111, 147, 231, 357, 481, 497, 562, 562-2, 624, 624-2, 674, 10066, 10100, 10130, 10130-1, 10130-2(bool), 10192, 10364, 10405, 10664, 10664-2, 10721, 10759, 11088, 11137, 11151, 12030, 12455

Math & Number Theory

583, 10104, 10179, 10299, 10780, 11064, 11466, 11889

Greedy

191, 195, 487, 657, 729, 10065, 10078, 10226, 10252, 10336, 10344, 10344-2, 10474, 10556, 10763, 10776, 10946, 11057, 11059, 11343, 11364, 11462, 11462-2, 11462-3, 11462-4, 11612, 11626, 11783, 12614, 12700

Backtracking

146, 195-2, 1079, 10098, 10344-3

Geometry

10525

Sorting & Searching

10611, 11876

Simulation & Ad Hoc

136, 167, 256, 260, 264, 264-2, 324, 350, 352, 369, 374, 382, 417, 441, 444, 445, 459, 469, 484, 490, 492, 495, 514, 541, 572, 574, 574-2nd, 574-3rd, 579, 621, 623, 673, 677, 696, 713, 727, 750, 782, 784, 785, 785-2, 871, 1056, 1056-2, 1112, 1124, 10017, 10048, 10093, 10099, 10110, 10127, 10189, 10190, 10212, 10223, 10263, 10279, 10282, 10282-2, 10295, 10300, 10300-2, 10324, 10334, 10347, 10370, 10394, 10420, 10432, 10452, 10469, 10494, 10494-2, 10515, 10533, 10550, 10579, 10583, 10608, 10673-1, 10673-2, 10685, 10703, 10773, 10783, 10922, 10935, 11029, 11044, 11085, 11220, 11223, 11244, 11344, 11349, 11470-2, 11498, 11526, 11541, 11561, 11648, 11723, 11728, 11879, 11942, 11942-2, 11953, 11960-2, 11965, 11965-2, 12114, 12149, 12157, 12243, 12279, 12289, 12342, 12372, 12416, 12555, 12555-2, 12577, 12578, 12592, 12608, 12643, 12646

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🟢 LightOJ

172 solutions in C++.

Graph

1003, 1009, 1026, 1034, 1046, 1063, 1066, 1101, 1111, 1141, 1168, 1174, 1175, 1185, 1210, 1238, 1257, 1263, 1291, 1300, 1300-2, 1337, 1348, 1348 [with comments], 1417

Dynamic Programming

1004, 1006, 1011, 1011-2, 1013, 1017, 1021, 1025, 1030, 1032, 1033, 1037, 1038, 1044, 1047, 1047 (2), 1051, 1051-2, 1057, 1064, 1068, 1110, 1110-2, 1119, 1140, 1157, 1157 (modified), 1157-2, 1157-3, 1158, 1159, 1169, 1191, 1217, 1231, 1283

Math & Number Theory

1005, 1007, 1024, 1027, 1028, 1048, 1054, 1065, 1067, 1076, 1077, 1083, 1085, 1089, 1098, 1112-BIT, 1114, 1129, 1135, 1148, 1163, 1166, 1183, 1183-2nd, 1187, 1187 (2), 1188, 1189, 1197, 1207, 1213, 1215, 1220, 1234, 1259, 1389, 1425

Data Structures

1083 [divide n conquer], 1224, 1339, 1424

Backtracking

1042, 1042-2

String

1039, 1039-2, 1255, 1258

Sorting & Searching

1127

Simulation & Ad Hoc

1008, 1010, 1012, 1014, 1016, 1020, 1022, 1023, 1035, 1043, 1045, 1049, 1049-1, 1053, 1062, 1069, 1072, 1078, 1080, 1082, 1087, 1088, 1090, 1093, 1094, 1096, 1107, 1109, 1112, 1113, 1116, 1122, 1131, 1133, 1136, 1138, 1164, 1164-2nd, 1182, 1186, 1192, 1198, 1202, 1212, 1214, 1225, 1227, 1235, 1236, 1241, 1247, 1249, 1253, 1266, 1282, 1294, 1307, 1338, 1354, 1387, 1393, 1414, 1882

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🟠 Codeforces

212 contests solved.

By Category:

Dynamic Programming

79C, 189A, 271D, 372B, 401D, 456C, 467C, 518D, 550C, 604C, 608C, 1363F, 1366C, 1382D, 1384B1, 1398D

Graph

230B, 274B, 275D, 369C, 377A, 378C, 385C, 412D, 427C, 475B, 584D, 588B, 688C, 1362D, 1363E, 1364D, 1366D, 1370C, 1372B, 1388C

Math & Number Theory

271B, 340A, 389A, 472A, 483A, 583C, 742C, 798C

Data Structures

1362B, 1368D, 1370B, 1375D

Greedy

375A, 376C, 389E, 413C

Sorting & Searching

1358D, 1366E

Contests:

3, 23, 31, 41, 52, 59, 61, 69, 71, 79, 95, 110, 112, 115, 116, 136, 189, 208, 217, 218, 230, 231, 236, 246, 253, 258, 260, 263, 265, 266, 268, 270, 271, 272, 274, 275, 276, 278, 281, 282, 284, 291, 294, 295, 296, 300, 302, 312, 313, 315, 318, 319, 330, 332, 334, 339, 340, 344, 347, 349, 350, 353, 355, 357, 358, 361, 362, 363, 366, 368, 369, 372, 375, 376, 377, 378, 379, 381, 382, 384, 385, 387, 389, 400, 401, 402, 404, 405, 412, 413, 416, 421, 427, 430, 432, 439, 441, 446, 450, 451, 452, 456, 459, 460, 462, 463, 465, 466, 467, 469, 472, 474, 475, 476, 478, 479, 483, 485, 486, 488, 489, 490, 492, 493, 494, 497, 499, 500, 507, 509, 513, 514, 516, 518, 519, 525, 526, 538, 550, 551, 555, 557, 567, 583, 584, 586, 588, 591, 593, 595, 604, 608, 610, 611, 614, 618, 624, 629, 631, 664, 670, 688, 701, 734, 735, 740, 742, 743, 747, 749, 752, 764, 765, 766, 768, 796, 798, 1118, 1140, 1162, 1341, 1342, 1343, 1345, 1348, 1352, 1353, 1354, 1358, 1359, 1360, 1362, 1363, 1364, 1365, 1366, 1367, 1368, 1369, 1370, 1371, 1372, 1373, 1374, 1375, 1380, 1382, 1384, 1388, 1389, 1391, 1398

Gym:100513

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🔴 SPOJ

20 solutions in C++.

Data Structures

#	Problem	Link
1043	GSS1	1043. GSS1.cpp
1043	GSS1 (2nd)	1043. GSS1-2nd.cpp
1716	GSS3	1716. GSS3.cpp
3267	DQUERY	3267. DQUERY.cpp
3693	KGSS	3693. KGSS.cpp
6256	INVCNT	6256. INVCNT.cpp
8002	Horrible	8002. Horrible.cpp
8060	AMR10F	8060 AMR10F.cpp

Dynamic Programming

#	Problem	Link
423	Assignments	423. Assignments.cpp

Graph

#	Problem	Link
913	QTREE2	913. QTREE2.cpp
14920	MST1	14920 MST1.cpp

Math & Number Theory

#	Problem	Link
78	Marbles	78. Marbles.cpp
4300	Rectangles	4300 Rectangles.cpp
—	DIVSUM	SPOJ DIVSUM.cpp

Greedy

#	Problem	Link
3921	BYTESE2	3921 BYTESE2.cpp

Sorting & Searching

#	Problem	Link
1837	Pie	1837 Pie.cpp

Simulation & Ad Hoc

#	Problem	Link
2123	Candy I	2123. Candy I.cpp
—	HELLOKIT	SPOJ HELLOKIT.cpp
—	VONNY	SPOJ VONNY.cpp
—	VONNY (2nd)	SPOJ VONNY-2.cpp

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🟣 TopCoder

55 problems solved in C++.

Dynamic Programming

EmoticonsDiv2, FoxAndMp3Easy, ListeningIn, NumberofFiboCalls, NumberofFiboCalls-1, PalindromicSubstringsDiv2, PlatformJumper, ShorterSuperSum, SumsOfPerfectPowers, ThePalindrome

Greedy

BinPacking, BinPackingEasy, Drbalance, SplitIntoPairs

String

DoubleLetter, EllysNewNickname, ErasingCharacters, FoxAndWord, InterestingNumber, SpamChecker, TaroString, TypingDistance

Math & Geometry

AlternateColors, BearPaints, BishopMove, BoundingBox, CandyMaking, LotteryTicket, RectangleCoveringEasy

Simulation & Ad Hoc

AlienAndPassword, BagsQuiz, CatsOnTheLineDiv2, Cdgame, DerivativeSequence, DistanceBetweenStrings, Egalitarianism3Easy, FibonacciDiv2, Haar1D, LeftAndRightHandedDiv2, LittleElephantAndBooks, LittleElephantAndDouble, LittleElephantAndString, MagicalStringDiv2, MicroStrings, MiddleCode, MysticAndCandiesEasy, OneDimensionalRobotEasy, PackingBallsDiv2, RobotHerbDiv2, SRMCards, SilverbachConjecture, TaroGrid, TypoCoderDiv2, WinterAndCandies, WinterAndMandarins