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