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combinatorics problems
Problem Name Online Judge Year Contest Difficulty Level
1 Marbles Categories SPOJ 1
2 Chocolate Categories Codeforces Codeforces Round #340 (Div. 2) 1
3 Number Sequence Categories PKU 1
4 Mashmokh and ACM Categories Codeforces Codeforces Round #240 (Div. 1) & Codeforces Round #240 (Div. 2) 1
5 Triangle Counting Categories UVA 1
6 Combinations Categories UVA 1
7 Wet Shark and Bishops Categories Codeforces Codeforces Round #341 (Div. 2) 1
8 Dreamoon and WiFi Categories Codeforces Codeforces Round #272 (Div. 2) 1
9 Random Teams Categories Codeforces Codeforces Round #273 (Div. 2) 1
10 Permutations Categories SPOJ 1
11 Pasha and Stick Categories Codeforces Codeforces Round #337 (Div. 2) 1
12 Cipher Categories PKU 1
13 Paths on a Grid Categories PKU 1
14 Wooden Sticks Categories PKU 1
15 DNA Sorting Categories PKU 1
16 Lucky Numbers Categories Codeforces Experimental Educational Round: VolBIT Formulas Blitz 1
17 Brick Wall Patterns Categories UVA 1
18 Round Numbers Categories PKU 1
19 Choose and divide Categories UVA 2
20 The World is a Theatre Categories Codeforces Codeforces Beta Round #95 (Div. 2) 2
21 Candy Distribution Categories PKU 2
22 How Many Trees? Categories UVA 2
23 Pocket Book Categories Codeforces Codeforces Round #108 (Div. 2) 2
24 Let it Bead Categories PKU 2
25 Ciel and Flowers Categories Codeforces Codeforces Round #190 (Div. 2) 2
26 How many nodes ? Categories UVA 2
27 Trees Made to Order Categories PKU 2
28 Leha and Function Categories Codeforces Codeforces Round #429 (Div. 1) & Codeforces Round #429 (Div. 2) 2
29 Necklace of Beads Categories PKU 2
30 Points on Line Categories Codeforces Codeforces Round #153 (Div. 1) & Codeforces Round #153 (Div. 2) 2
31 Count the Trees Categories UVA 2
32 Color Categories PKU 2
33 Mr. Kitayuta's Gift Categories Codeforces Codeforces Round #286 (Div. 1) & Codeforces Round #286 (Div. 2) & Codeforces Round #286 (Div. 1) & Codeforces Round #286 (Div. 2) 2
34 Yet another Number Sequence Categories UVA 2
35 Modulo Sum Categories Codeforces Codeforces Round #319 (Div. 2) 2
36 Safe Salutations Categories UVA 2
37 Permutations Categories UVA 2
38 Code Categories PKU 2
39 Kyoya and Colored Balls Categories Codeforces Codeforces Round #309 (Div. 1) & Codeforces Round #309 (Div. 2) 2
40 Kolya and Tanya Categories Codeforces Codeforces Round #324 (Div. 2) 2
41 Longge's problem Categories PKU 3
42 Cow Sorting Categories PKU 3
43 Burger Categories UVA 3
44 Selection of Personnel Categories Codeforces Experimental Educational Round: VolBIT Formulas Blitz 3
45 Lucky tickets Categories PKU 3
46 Connected Graph Categories PKU 3
47 A decorative fence Categories PKU 3
48 Hamming Distance Sum Categories Codeforces Codeforces Round #336 (Div. 2) 3
49 Binomial Theorem Categories UVA 3
50 Little Elephant and Interval Categories Codeforces Codeforces Round #129 (Div. 1) & Codeforces Round #129 (Div. 2) 3
51 Card Game Categories SPOJ 3
52 Ilya and Escalator Categories Codeforces Codeforces Round #293 (Div. 2) 3
53 Magic Bracelet Categories PKU 3
54 Pashmak and Buses Categories Codeforces Codeforces Round #261 (Div. 2) 3
55 Expression Bracketing Categories UVA 3
56 Unbearable Controversy of Being Categories Codeforces Codeforces Round #277.5 (Div. 2) 3
57 The Intriguing Obsession Categories Codeforces Codeforces Round #439 (Div. 2) 4
58 Leonardo's Notebook Categories PKU 4
59 Inna and Nine Categories Codeforces Codeforces Round #220 (Div. 2) 4
60 Beautiful Numbers Categories Codeforces Codeforces Round #181 (Div. 2) 4
61 Tourist Problem Categories Codeforces Codeforces Round #198 (Div. 2) & Codeforces Round #198 (Div. 1) 4
62 New Year Santa Network Categories Codeforces Good Bye 2014 4
63 CARDS Categories PKU 4
64 Dima and Sequence Categories Codeforces Codeforces Round #167 (Div. 2) 4
65 Directed Roads Categories Codeforces Codeforces Round #369 (Div. 2) 4
66 Benches Categories Codeforces Experimental Educational Round: VolBIT Formulas Blitz 4
67 Gerald and Giant Chess Categories Codeforces Codeforces Round #313 (Div. 1) & Codeforces Round #313 (Div. 2) 4
68 Difference between Triplets Categories PKU 4
69 Magic Five Categories Codeforces Codeforces Round #191 (Div. 2) 4
70 Matrix Categories Codeforces Codeforces Round #213 (Div. 1) & Codeforces Round #213 (Div. 2) 4
71 Vanya and Triangles Categories Codeforces Codeforces Round #308 (Div. 2) 4
72 The Stable Marriage Problem Categories PKU 4
73 Ralph And His Magic Field Categories Codeforces Codeforces Round #447 (Div. 2) 4
74 FUN WITH NUMBERS Categories SPOJ 4
75 Polo the Penguin and Houses Categories Codeforces Codeforces Round #177 (Div. 1) 4
76 Star Categories Codeforces April Fools Day Contest 4
77 Weather Categories Codeforces Codeforces Round #145 (Div. 2, ACM-ICPC Rules) 4
78 Quantity of Strings Categories Codeforces Codeforces Round #107 (Div. 1) & Codeforces Round #107 (Div. 2) 4
79 Malek Dance Club Categories Codeforces Codeforces Round #189 (Div. 1) & Codeforces Round #189 (Div. 2) 5
80 Two Heaps Categories Codeforces Codeforces Round #205 (Div. 2) 5
81 Increase Sequence Categories Codeforces Codeforces Round #266 (Div. 2) 5
82 How many trees? Categories Codeforces Codeforces Beta Round #9 (Div. 2 Only) 5
83 Kyoya and Permutation Categories Codeforces Codeforces Round #309 (Div. 1) & Codeforces Round #309 (Div. 2) 5
84 Weird journey Categories Codeforces Codeforces Round #407 (Div. 1) & Codeforces Round #407 (Div. 2) 5
85 Lengthening Sticks Categories Codeforces Codeforces Round #317 [AimFund Thanks-Round] (Div. 1) & Codeforces Round #317 [AimFund Thanks-Round] (Div. 2) 5
86 Mashmokh and Reverse Operation Categories Codeforces Codeforces Round #240 (Div. 1) & Codeforces Round #240 (Div. 2) 5
87 Square Subsets Categories Codeforces Codeforces Round #448 (Div. 2) 5
88 Vitaly and Cycle Categories Codeforces Codeforces Round #311 (Div. 2) 5
89 Cycles Categories Codeforces Codeforces Round #144 (Div. 1) & Codeforces Round #144 (Div. 2) 5
90 Shaass and Lights Categories Codeforces Codeforces Round #178 (Div. 2) 5
91 Basketball Team Categories Codeforces Codeforces Beta Round #83 (Div. 1 Only) & Codeforces Beta Round #83 (Div. 2 Only) 5
92 Iahub and Permutations Categories Codeforces Codeforces Round #198 (Div. 2) & Codeforces Round #198 (Div. 1) 5
93 Permutations Categories Codeforces Codeforces Beta Round #92 (Div. 2 Only) 5
94 Roman and Numbers Categories Codeforces Codeforces Round #235 (Div. 2) 5
95 Jerry's Protest Categories Codeforces 8VC Venture Cup 2016 - Elimination Round 5
96 Anton and School - 2 Categories Codeforces Codeforces Round #404 (Div. 2) 5
97 Jeff and Furik Categories Codeforces Codeforces Round #204 (Div. 1) & Codeforces Round #204 (Div. 2) 5
98 Symmetric and Transitive Categories Codeforces Codeforces Round #315 (Div. 1) & Codeforces Round #315 (Div. 2) 5
99 Games with Rectangle Categories Codeforces Codeforces Beta Round #94 (Div. 1 Only) & Codeforces Beta Round #94 (Div. 2 Only) 5
100 Regetni Categories PKU 5
101 Winter is here Categories Codeforces Codeforces Round #428 (Div. 2) 5
102 Prime Factors Categories Live Archive 1997 North America - East Central NA 5
103 The shuffle Problem Categories PKU 5
104 Dima and Two Sequences Categories Codeforces Codeforces Round #167 (Div. 2) & Codeforces Round #167 (Div. 1) 5
105 Jzzhu and Numbers Categories Codeforces Codeforces Round #257 (Div. 1) 6
106 Triangles Categories Codeforces Codeforces Round #142 (Div. 1) & Codeforces Round #142 (Div. 2) 6
107 Pig and Palindromes Categories Codeforces Codeforces Round #316 (Div. 2) 6
108 Array Categories Codeforces Codeforces Beta Round #53 6
109 Little Elephant and Elections Categories Codeforces Codeforces Round #157 (Div. 1) & Codeforces Round #157 (Div. 2) 6
110 Unusual Sequences Categories Codeforces Codeforces Round #450 (Div. 2) 6
111 Special Matrices Categories Codeforces Codeforces Round #277.5 (Div. 2) 6
112 Lucky Permutation Categories Codeforces Codeforces Beta Round #91 (Div. 1 Only) & Codeforces Beta Round #91 (Div. 2 Only) 6
113 Devu and Flowers Categories Codeforces Codeforces Round #258 (Div. 2) 6
114 Compartments Categories Codeforces Codeforces Round #207 (Div. 1) & Codeforces Round #207 (Div. 2) 6
115 Memory and Scores Categories Codeforces Codeforces Round #370 (Div. 2) 6
116 Pluses everywhere Categories Codeforces Codeforces Round #295 (Div. 2) & Codeforces Round #295 (Div. 1) 6
117 Sum of powers Categories PKU 6
118 ETS Problem setting Categories UVA 6
119 Challenge Pennants Categories Codeforces Experimental Educational Round: VolBIT Formulas Blitz 6
120 Cipher Categories Codeforces Codeforces Round #110 (Div. 1) & Codeforces Round #110 (Div. 2) 6
121 Magic Trick Categories Codeforces MemSQL Start[c]UP 2.0 - Round 1 6
122 Mike and Geometry Problem Categories Codeforces Codeforces Round #361 (Div. 2) 6
123 GukiZ and Binary Operations Categories Codeforces Codeforces Round #307 (Div. 2) 6
124 Bots Categories Codeforces Bubble Cup 8 - Finals [Online Mirror] 6
125 Lucky Subsequence Categories Codeforces Codeforces Round #104 (Div. 1) & Codeforces Round #104 (Div. 2) 6
126 Birthday Cake Categories PKU 6
127 Random Task Categories Codeforces Codeforces Round #247 (Div. 2) 6
128 Partial Sums Categories Codeforces Codeforces Round #138 (Div. 1) & Codeforces Round #138 (Div. 2) 6
129 Permutation Sum Categories Codeforces Codeforces Round #175 (Div. 2) 6
130 Table Categories Codeforces Codeforces Round #144 (Div. 1) & Codeforces Round #144 (Div. 2) 6
131 Numbers Categories Codeforces Codeforces Round #131 (Div. 1) & Codeforces Round #131 (Div. 2) 6
132 Greg and Friends Categories Codeforces Codeforces Round #179 (Div. 1) & Codeforces Round #179 (Div. 2) 6
133 Little Elephant and LCM Categories Codeforces Codeforces Round #157 (Div. 1) & Codeforces Round #157 (Div. 2) 6
134 Parking Lot Categories Codeforces Experimental Educational Round: VolBIT Formulas Blitz 6
135 String Mark Categories Codeforces Codeforces Round #448 (Div. 2) 7
136 Yaroslav and Two Strings Categories Codeforces Codeforces Round #179 (Div. 2) 7
137 Dima and Horses Categories Codeforces Codeforces Round #167 (Div. 2) & Codeforces Round #167 (Div. 1) 7
138 Chessboard Billiard Categories Codeforces Codeforces Beta Round #68 7
139 Ski Base Categories Codeforces Codeforces Beta Round #75 (Div. 1 Only) & Codeforces Beta Round #75 (Div. 2 Only) 7
140 Fence Divercity Categories Codeforces Codeforces Round #346 (Div. 2) 7
141 ????? Categories PKU 7
142 Levko and Strings Categories Codeforces Codeforces Round #210 (Div. 1) & Codeforces Round #210 (Div. 2) 7
143 Plato's Blocks Categories PKU 7
144 On Number of Decompositions into Multipliers Categories Codeforces Codeforces Round #232 (Div. 1) & Codeforces Round #232 (Div. 2) 7
145 Axis Walking Categories Codeforces Codeforces Round #191 (Div. 2) 7
146 Devu and Birthday Celebration Categories Codeforces Codeforces Round #251 (Div. 2) 7
147 Square Root of Permutation Categories Codeforces Educational Codeforces Round 4 7
148 The table Categories Codeforces Codeforces Round #140 (Div. 1) 7
149 Right Triangles Categories Codeforces Codeforces Testing Round #1 7
150 Beautiful Pairs of Numbers Categories Codeforces Codeforces Round #236 (Div. 1) 7
151 Vasily the Bear and Beautiful Strings Categories Codeforces Codeforces Round #195 (Div. 2) 7
152 On the Bench Categories Codeforces Codeforces Round #429 (Div. 1) & Codeforces Round #429 (Div. 2) 7
153 Bath Queue Categories Codeforces Codeforces Beta Round #28 (Codeforces format) 8
154 Cowslip Collections Categories Codeforces CROC 2016 - Elimination Round 8
155 Vowels Categories Codeforces Codeforces Round #225 (Div. 1) 8
156 Positions in Permutations Categories Codeforces Codeforces Round #175 (Div. 2) 8
157 Polo the Penguin and Trees Categories Codeforces Codeforces Round #177 (Div. 1) 8
158 Playing with Superglue Categories Codeforces Croc Champ 2012 - Round 2 8
159 Number Table Categories Codeforces Codeforces Beta Round #39 8
160 Black-and-White Cube Categories Codeforces Testing Round #7 8
161 Gifts Categories Codeforces Codeforces Round #142 (Div. 1) 8
162 Distinct Paths Categories Codeforces Croc Champ 2013 - Round 2 8
163 New Year Garland Categories Codeforces Codeforces Round #100 8
164 Cow Tennis Tournament Categories Codeforces Codeforces Round #174 (Div. 1) 8
165 Brackets Categories Codeforces Codeforces Beta Round #92 (Div. 1 Only) & Codeforces Beta Round #92 (Div. 2 Only) 8
166 Parquet Categories Codeforces Codeforces Beta Round #26 (Codeforces format) 8
167 Olya and Graph Categories Codeforces Codeforces Round #184 (Div. 2) 8
168 Misha and Palindrome Degree Categories Codeforces Codeforces Round #285 (Div. 2) & Codeforces Round #285 (Div. 1) 8
169 Clues Categories Codeforces Codeforces Round #110 (Div. 1) 8
170 Different Subsets For All Tuples Categories Codeforces Educational Codeforces Round 11 8
171 The Child and Binary Tree Categories Codeforces Codeforces Round #250 (Div. 1) 8
172 Find a car Categories Codeforces Codeforces Round #415 (Div. 1) & Codeforces Round #415 (Div. 2) 8
173 Petya and Coloring Categories Codeforces Codeforces Beta Round #85 (Div. 1 Only) 8
174 Tickets Categories Codeforces Codeforces Beta Round #26 (Codeforces format) 8
175 Hexagonal Routes Categories PKU 8
176 An unavoidable detour for home Categories Codeforces Codeforces Round #418 (Div. 2) 8
177 Codeword Categories Codeforces Codeforces Round #349 (Div. 1) 8
178 Sereja and Intervals Categories Codeforces Codeforces Round #215 (Div. 1) 8
179 Number Challenge Categories Codeforces Codeforces Round #146 (Div. 1) 8
180 Periodical Numbers Categories Codeforces Codeforces Round #132 (Div. 2) 8
181 Greg and Caves Categories Codeforces Codeforces Round #179 (Div. 1) 8
182 Pasha and Pipe Categories Codeforces Codeforces Round #293 (Div. 2) 9
183 Lust Categories Codeforces Codeforces Round #446 (Div. 1) 9
184 Bitonix' Patrol Categories Codeforces Codeforces Round #134 (Div. 1) 9
185 Present for Vitalik the Philatelist Categories Codeforces Codeforces Round #325 (Div. 1) 9
186 Lesson Timetable Categories Codeforces Codeforces Beta Round #37 9
187 Move by Prime Categories Codeforces IndiaHacks 2016 - Online Edition (Div. 1 + Div. 2) 9
188 Yet Another Number Sequence Categories Codeforces Codeforces Round #230 (Div. 1) & Codeforces Round #230 (Div. 2) 9
189 Flags Categories Codeforces Codeforces Beta Round #76 (Div. 1 Only) 9
190 Thoroughly Bureaucratic Organization Categories Codeforces Codeforces Round #127 (Div. 1) 9
191 Karen and Cards Categories Codeforces Codeforces Round #419 (Div. 1) 9
192 Triangles Categories Codeforces Codeforces Beta Round #15 9
193 Little Elephant and Triangle Categories Codeforces Codeforces Round #136 (Div. 1) 9
194 On Sum of Number of Inversions in Permutations Categories Codeforces Codeforces Round #232 (Div. 1) 9
195 Transforming Sequence Categories Codeforces AIM Tech Round (Div. 1) 9
196 The Red Button Categories Codeforces MemSQL start[c]up Round 1 9
197 Singer House Categories Codeforces Codeforces Round #424 (Div. 1, rated, based on VK Cup Finals) 9
198 Sereja and Cinema Categories Codeforces Codeforces Round #223 (Div. 1) 9
199 Research Rover Categories Codeforces Intel Code Challenge Elimination Round (Div. 1 + Div. 2, combined) 9
200 Pentagon Categories Codeforces Codeforces Beta Round #48 9
201 Lucky Pair Categories Codeforces Codeforces Round #104 (Div. 1) 9
202 Random Function and Tree Categories Codeforces Codeforces Round #275 (Div. 1) 9
203 Ksenia and Combinatorics Categories Codeforces Codeforces Round #224 (Div. 2) 9
204 Randomizer Categories Codeforces Codeforces Round #313 (Div. 1) 9
205 White, Black and White Again Categories Codeforces Testing Round #6 9
206 Weak Subsequence Categories Codeforces Codeforces Beta Round #97 (Div. 1) 10
207 Drawing Circles is Fun Categories Codeforces Codeforces Round #219 (Div. 1) 10
208 Vasily the Bear and Painting Square Categories Codeforces Codeforces Round #195 (Div. 2) 10
209 Days of Floral Colours Categories Codeforces Codeforces Round #431 (Div. 1) 10
210 Numbers on the blackboard Categories Codeforces Codeforces Round #443 (Div. 1) 10
211 Toys Categories Codeforces School Team Contest #2 (Winter Computer School 2010/11) 10
212 Bingo! Categories Codeforces MemSQL Start[c]UP 2.0 - Round 2 10
213 Shake It! Categories Codeforces Codeforces Round #431 (Div. 1) 10
214 Nephren Runs a Cinema Categories Codeforces Codeforces Round #449 (Div. 1) 10
215 Sleeping Categories Codeforces Codeforces Beta Round #86 (Div. 1 Only) 10