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