Number Theory

Problem Name Online Judge Year Contest Difficulty Level
1 Twin Primes UVA 1
2 Goldbach's Conjecture UVA 1
3 Play with Floor and Ceil UVA 1
4 Alyona and Numbers Codeforces Codeforces Round #358 (Div. 2) 1
5 Prime Generator SPOJ 1
6 Ones UVA 1
7 LCM Sum SPOJ 1
8 T-primes Codeforces Codeforces Round #142 (Div. 2) 1
9 String Task Codeforces Codeforces Beta Round #89 (Div. 2) 1
10 Again Twenty Five! Codeforces Experimental Educational Round: VolBIT Formulas Blitz 1
11 Prime Number Theorem SPOJ 1
12 Bear and Poker Codeforces Codeforces Round #318 [RussianCodeCup Thanks-Round] (Div. 1) & Codeforces Round #318 [RussianCodeCup Thanks-Round] (Div. 2) 1
13 The Moronic Cowmpouter SPOJ 1
14 Almost Prime Codeforces Codeforces Beta Round #26 (Codeforces format) 1
15 A and B and Team Training Codeforces Codeforces Round #294 (Div. 2) 1
16 Divisor Summation SPOJ 1
17 Prime Cuts UVA 1
18 Fedya and Maths Codeforces Codeforces Round #260 (Div. 2) 1
19 Almost Prime Numbers UVA 1
20 Hexadecimal's theorem Codeforces Codeforces Round #125 (Div. 2) 1
21 Factorial SPOJ 1
22 Prime or Not SPOJ 1
23 Toy Army Codeforces Codeforces Beta Round #72 (Div. 2 Only) 1
24 Arpa’s hard exam and Mehrdad’s naive cheat Codeforces Codeforces Round #383 (Div. 2) 1
25 Fombinatorial CodeChef 1
26 Ilya and Bank Account Codeforces Codeforces Round #186 (Div. 2) 1
27 Simply Emirp UVA 1
28 Design Tutorial: Learn from Math Codeforces Codeforces Round #270 1
29 Graph Connectivity UVA 1
30 Two squares or not two squares SPOJ 1
31 The Equation SGU 1
32 Euler Totient Function SPOJ 1
33 GCD Extreme SPOJ 1
34 The primary problem UVA 1
35 Tip Top Game SPOJ 1
36 Bachgold Problem Codeforces Codeforces Round #388 (Div. 2) 1
37 Factors and Factorials UVA 1
38 Factorial Live Archive 2000 Europe - Central 1
39 Panoramix's Prediction Codeforces Codeforces Beta Round #69 (Div. 2 Only) 1
40 Vasya and Petya's Game Codeforces Codeforces Round #319 (Div. 1) & Codeforces Round #319 (Div. 2) 1
41 Lucky Division Codeforces Codeforces Beta Round #91 (Div. 2 Only) 1
42 Marbles SPOJ 1
43 Cifera Codeforces Codeforces Beta Round #86 (Div. 2 Only) 1
44 Divisors SPOJ 1
45 Prime Words UVA 1
46 Integer Factorization (15 digits) SPOJ 1
47 Goldbach's Conjecture (II) UVA 1
48 Count the factors TJU 1
49 Totient Extreme SPOJ 1
50 Multiplication Table Codeforces Codeforces Round #319 (Div. 2) 1
51 Game of Lines SPOJ 1
52 Medium Factorization SPOJ 1
53 Relatives UVA 1
54 Factovisors UVA 1
55 Celebrity jeopardy UVA 1
56 Drazil and His Happy Friends Codeforces Codeforces Round #292 (Div. 1) & Codeforces Round #292 (Div. 2) & Codeforces Round #292 (Div. 1) & Codeforces Round #292 (Div. 2) 2
57 Divisor Summation (Hard) SPOJ 2
58 Odd Numbers of Divisors SPOJ 2
59 Sort fractions SPOJ 2
60 Pride Codeforces Codeforces Round #446 (Div. 1) & Codeforces Round #446 (Div. 2) 2
61 Vladik and fractions Codeforces Codeforces Round #384 (Div. 2) 2
62 Goldbach and Euler UVA 2
63 Playing with Marbles SPOJ 2
64 Psycho SPOJ 2
65 Mr. Azad and his Son!!!!! UVA 2
66 Marbles UVA 2
67 Taxes Codeforces Codeforces Round #382 (Div. 2) & Codeforces Round #382 (Div. 1) 2
68 Minimum Number SPOJ 2
69 TEX Quotes Live Archive 1994 North America - East Central NA 2
70 LCM Challenge Codeforces Codeforces Round #146 (Div. 1) & Codeforces Round #146 (Div. 2) 2
71 Number Theory for Newbies UVA 2
72 Dima and Lisa Codeforces Codeforces Round #324 (Div. 2) 2
73 Prime Matrix Codeforces Codeforces Round #166 (Div. 2) 2
74 Rational Resistance Codeforces Codeforces Round #200 (Div. 1) & Codeforces Round #200 (Div. 2) 2
75 Mashmokh and Numbers Codeforces Codeforces Round #240 (Div. 1) & Codeforces Round #240 (Div. 2) 2
76 Integer Factorization (20 digits) SPOJ 2
77 Jumping Champion UVA 2
78 Leha and Function Codeforces Codeforces Round #429 (Div. 1) & Codeforces Round #429 (Div. 2) 2
79 Square-free integers SPOJ 2
80 Mint UVA 2
81 Equation SPOJ 2
82 Alice and Bob Codeforces Codeforces Round #201 (Div. 1) & Codeforces Round #201 (Div. 2) 2
83 MCQ Exam A2 Online Judge 2
84 Arpa’s obvious problem and Mehrdad’s terrible solution Codeforces Codeforces Round #383 (Div. 2) 2
85 Anagrammatic Primes UVA 2
86 Ice Sculptures Codeforces VK Cup 2012 Qualification Round 1 2
87 Prime Again SPOJ 2
88 Divisors 2 SPOJ 2
89 k-th divisor Codeforces Educational Codeforces Round 17 2
90 Soldier and Number Game Codeforces Codeforces Round #304 (Div. 2) 2
91 Primitive Root SPOJ 2
92 N DIV PHI_N SPOJ 2
93 Pythagorean Triples Codeforces Codeforces Round #368 (Div. 2) 2
94 The Bytelandian Cryptographer (Act I) SPOJ 2
95 Congruence Equation SPOJ 3
96 Good Sequences Codeforces Codeforces Round #162 (Div. 1) & Codeforces Round #162 (Div. 2) 3
97 Primal Fear SPOJ 3
98 Cows and Primitive Roots Codeforces Codeforces Round #174 (Div. 2) 3
99 Eugeny and Play List Codeforces Codeforces Round #182 (Div. 2) 3
100 Primes on Interval Codeforces Codeforces Round #147 (Div. 2) 3
101 Sky Code SPOJ 3
102 Little Elephant and Numbers Codeforces Codeforces Round #136 (Div. 2) 3
103 Modified GCD Codeforces Codeforces Beta Round #67 (Div. 2) 3
104 Fox Dividing Cheese Codeforces Codeforces Round #218 (Div. 2) 3
105 DDF UVA 3
106 Win or Freeze Codeforces Codeforces Round #107 (Div. 1) & Codeforces Round #107 (Div. 2) 3
107 Homework SPOJ 3
108 GCD Determinant SPOJ 3
109 Binomial Coefficients SPOJ 3
110 Chef and Functions CodeChef 3
111 Mike and gcd problem Codeforces Codeforces Round #410 (Div. 2) 3
112 The Super Powers UVA 3
113 A Trivial Problem Codeforces Manthan, Codefest 16 3
114 Bear and Prime Numbers Codeforces Codeforces Round #226 (Div. 2) 3
115 Skyscraper Floors SPOJ 3
116 Noldbach problem Codeforces Codeforces Beta Round #17 3
117 Levko and Permutation Codeforces Codeforces Round #210 (Div. 2) 3
118 Easy Number Challenge Codeforces Codeforces Round #146 (Div. 2) 3
119 Quiz Codeforces Codeforces Round #196 (Div. 2) & Codeforces Round #196 (Div. 1) 3
120 Routine Problem Codeforces Codeforces Round #196 (Div. 2) 3
121 Permutation Primes Live Archive 2004 Asia - Dhaka 3
122 The Meaningless Game Codeforces Codeforces Round #426 (Div. 1) & Codeforces Round #426 (Div. 2) 3
123 Primes or Palindromes? Codeforces Codeforces Round #315 (Div. 1) & Codeforces Round #315 (Div. 2) 3
124 Petya and Divisors Codeforces Codeforces Beta Round #85 (Div. 1 Only) & Codeforces Beta Round #85 (Div. 2 Only) 4
125 SETI SPOJ 4
126 Devu and Partitioning of the Array Codeforces Codeforces Round #251 (Div. 2) 4
127 Dots SPOJ 4
128 Skyscraper Floors UVA 4
129 Find Maximum Codeforces Codeforces Round #205 (Div. 2) 4
130 Broken Keyboard UVA 4
131 Subtractions Codeforces Codeforces Testing Round #5 4
132 Chilly Willy Codeforces Codeforces Round #152 (Div. 2) 4
133 Ralph And His Magic Field Codeforces Codeforces Round #447 (Div. 2) 4
134 The Most Complex Number Timus 4
135 Irrational problem Codeforces Codeforces Beta Round #62 4
136 Rank of a Fraction SPOJ 4
137 Divisible by Seven Codeforces Codeforces Round #221 (Div. 1) & Codeforces Round #221 (Div. 2) 4
138 Subtraction A2 Online Judge 4
139 Colliders Codeforces Codeforces Round #109 (Div. 1) & Codeforces Round #109 (Div. 2) 4
140 Multipliers Codeforces Codeforces Round #338 (Div. 2) 4
141 Round Table Knights Codeforces Codeforces Beta Round #65 (Div. 2) 4
142 Gerald and Giant Chess Codeforces Codeforces Round #313 (Div. 1) & Codeforces Round #313 (Div. 2) 4
143 Well-known Numbers Codeforces Codeforces Round #139 (Div. 2) 4
144 Ant colony Codeforces Codeforces Round #271 (Div. 2) 4
145 Fox And Jumping Codeforces Codeforces Round #290 (Div. 2) & Codeforces Round #290 (Div. 1) 4
146 Boring Card Game Live Archive 2011 Europe - Central 4
147 Ksusha and Array Codeforces Croc Champ 2013 - Round 2 (Div. 2 Edition) 4
148 N DIV PHI_N (Hard) SPOJ 4
149 Gaussian Prime Factors Live Archive 2006 Asia - Manila 4
150 Remainders Game Codeforces Codeforces Round #360 (Div. 1) & Codeforces Round #360 (Div. 2) 4
151 Fortune Telling Codeforces Codeforces Beta Round #55 (Div. 2) 4
152 Petya and His Friends Codeforces Codeforces Beta Round #61 (Div. 2) 5
153 Mike and Foam Codeforces Codeforces Round #305 (Div. 1) & Codeforces Round #305 (Div. 2) 5
154 Line Codeforces Codeforces Beta Round #7 5
155 Chocolate Codeforces Codeforces Round #279 (Div. 2) 5
156 Moodular Arithmetic Codeforces Codeforces Round #334 (Div. 1) & Codeforces Round #334 (Div. 2) 5
157 Shaass and Lights Codeforces Codeforces Round #178 (Div. 2) 5
158 Array and Operations Codeforces Codeforces Round #284 (Div. 1) & Codeforces Round #284 (Div. 2) 5
159 Roman and Numbers Codeforces Codeforces Round #235 (Div. 2) 5
160 Vasya and Beautiful Arrays Codeforces Codeforces Round #206 (Div. 1) & Codeforces Round #206 (Div. 2) 5
161 Rectangular Game Codeforces ABBYY Cup 2.0 - Easy 5
162 Number With The Given Amount Of Divisors Codeforces Codeforces Beta Round #27 (Codeforces format, Div. 2) 5
163 Upgrading Array Codeforces Codeforces Round #236 (Div. 2) & Codeforces Round #236 (Div. 1) 5
164 Monitor Codeforces Codeforces Beta Round #16 (Div. 2 Only) 5
165 Rectangular Game Codeforces ABBYY Cup 2.0 - Easy 5
166 Vasily the Bear and Sequence Codeforces Codeforces Round #195 (Div. 2) 5
167 Anton and School - 2 Codeforces Codeforces Round #404 (Div. 2) 5
168 Tutorial BFS SPOJ 5
169 Clique in the Divisibility Graph Codeforces VK Cup 2015 - Finals, online mirror 5
170 Winter is here Codeforces Codeforces Round #428 (Div. 2) 5
171 Prime Permutation Codeforces Codeforces Beta Round #92 (Div. 1 Only) & Codeforces Beta Round #92 (Div. 2 Only) 5
172 Palindrome Degree Codeforces Codeforces Beta Round #7 5
173 Pseudorandom Sequence Period Codeforces Croc Champ 2012 - Qualification Round 5
174 Devu and Flowers Codeforces Codeforces Round #258 (Div. 2) 6
175 Unusual Sequences Codeforces Codeforces Round #450 (Div. 2) 6
176 Beautiful numbers Codeforces Codeforces Beta Round #51 6
177 Printing some primes (Hard) SPOJ 6
178 Calendar Reform Codeforces Croc Champ 2012 - Qualification Round 6
179 DZY Loves Fibonacci Numbers Codeforces Codeforces Round #255 (Div. 1) & Codeforces Round #255 (Div. 2) 6
180 GukiZ and Binary Operations Codeforces Codeforces Round #307 (Div. 2) 6
181 Reducing Fractions Codeforces Codeforces Round #137 (Div. 2) 6
182 Longest Subsequence Codeforces Educational Codeforces Round 9 6
183 Beaver Game Codeforces Codeforces Beta Round #70 (Div. 2) 6
184 Bots Codeforces Bubble Cup 8 - Finals [Online Mirror] 6
185 Very Interesting Game Codeforces Codeforces Beta Round #88 6
186 Pluses everywhere Codeforces Codeforces Round #295 (Div. 2) & Codeforces Round #295 (Div. 1) 6
187 Divisors Codeforces Codeforces Round #256 (Div. 2) 6
188 Goldbach++ Live Archive 2005 North America - Southeast USA 6
189 ZS and The Birthday Paradox Codeforces Codeforces Round #369 (Div. 2) 6
190 Polygon Encoder SPOJ 6
191 Lucky Permutation Codeforces Codeforces Beta Round #91 (Div. 1 Only) & Codeforces Beta Round #91 (Div. 2 Only) 6
192 Jzzhu and Apples Codeforces Codeforces Round #257 (Div. 1) & Codeforces Round #257 (Div. 2) 6
193 Prefix Product Sequence Codeforces Codeforces Round #278 (Div. 1) & Codeforces Round #278 (Div. 2) 6
194 Apple Tree Codeforces Codeforces Round #202 (Div. 1) & Codeforces Round #202 (Div. 2) 6
195 Array GCD Codeforces AIM Tech Round (Div. 1) & AIM Tech Round (Div. 2) 6
196 Divisor Tree Codeforces Codeforces Round #196 (Div. 2) & Codeforces Round #196 (Div. 1) 7
197 Pairs of Numbers Codeforces Codeforces Testing Round #3 7
198 On Sum of Fractions Codeforces Codeforces Round #232 (Div. 1) & Codeforces Round #232 (Div. 2) 7
199 Double Happiness Codeforces Codeforces Beta Round #86 (Div. 1 Only) & Codeforces Beta Round #86 (Div. 2 Only) 7
200 Digital Root Codeforces Codeforces Beta Round #10 7
201 Integer Factorization (29 digits) SPOJ 7
202 Number Transformation Codeforces Codeforces Round #153 (Div. 1) & Codeforces Round #153 (Div. 2) 7
203 Traffic Jams in the Land Codeforces Codeforces Round #284 (Div. 1) 7
204 Alice, Bob, Oranges and Apples Codeforces Codeforces Round #325 (Div. 1) & Codeforces Round #325 (Div. 2) 7
205 Bamboo Partition Codeforces Codeforces Round #424 (Div. 1, rated, based on VK Cup Finals) & Codeforces Round #424 (Div. 2, rated, based on VK Cup Finals) 7
206 Sum of Remainders Codeforces Educational Codeforces Round 5 7
207 ucyhf Codeforces April Fools Day Contest 7
208 On Number of Decompositions into Multipliers Codeforces Codeforces Round #232 (Div. 1) & Codeforces Round #232 (Div. 2) 7
209 Finding the Kth Prime (Hard) SPOJ 7
210 Chessboard Billiard Codeforces Codeforces Beta Round #68 7
211 Notepad Codeforces Codeforces Beta Round #17 8
212 Beautiful Set Codeforces Codeforces Round #213 (Div. 1) & Codeforces Round #213 (Div. 2) 8
213 Superior Periodic Subarrays Codeforces Codeforces Round #323 (Div. 1) & Codeforces Round #323 (Div. 2) 8
214 REQ Codeforces Codeforces Round #330 (Div. 1) 8
215 Cube Problem Codeforces Croc Champ 2013 - Round 2 8
216 Mishka and Divisors Codeforces Codeforces Round #365 (Div. 2) 8
217 Ultimate Weirdness of an Array Codeforces Codeforces Round #352 (Div. 1) & Codeforces Round #352 (Div. 2) 8
218 GCD Table Codeforces Codeforces Round #196 (Div. 1) 8
219 Timofey and remoduling Codeforces Codeforces Round #395 (Div. 1) & Codeforces Round #395 (Div. 2) 8
220 Fractions UVA 8
221 Number Challenge Codeforces Codeforces Round #146 (Div. 1) 8
222 Prime Problem Codeforces School Team Contest #3 (Winter Computer School 2010/11) 8
223 Three Horses Codeforces Codeforces Round #166 (Div. 2) 8
224 Periodical Numbers Codeforces Codeforces Round #132 (Div. 2) 8
225 Numbers Codeforces Codeforces Beta Round #72 (Div. 1 Only) 8
226 The Child and Binary Tree Codeforces Codeforces Round #250 (Div. 1) 8
227 Unsolvable Codeforces Codeforces Round #139 (Div. 2) 8
228 Ada and Connections SPOJ 8
229 Cowslip Collections Codeforces CROC 2016 - Elimination Round 8
230 Cows and Cool Sequences Codeforces Codeforces Round #174 (Div. 1) 8
231 Martian Luck Codeforces Codeforces Round #133 (Div. 2) 8
232 Anniversary Codeforces Codeforces Round #140 (Div. 1) & Codeforces Round #140 (Div. 2) 8
233 Rotatable Number Codeforces Codeforces Round #183 (Div. 1) 9
234 Visit of the Great Codeforces Codeforces Round #118 (Div. 1) 9
235 Four Divisors Codeforces Educational Codeforces Round 12 9
236 White, Black and White Again Codeforces Testing Round #6 9
237 Swap (Easy - Level 2) SPOJ 9
238 Tractor College Codeforces Codeforces Round #126 (Div. 2) 9
239 Shaass and Painter Robot Codeforces Codeforces Round #178 (Div. 2) 9
240 Levko and Sets Codeforces Codeforces Round #210 (Div. 1) 9
241 Superhero's Job Codeforces VK Cup 2015 - Round 3 (unofficial online mirror, Div. 1 only) 9
242 Morrowindows Codeforces Codeforces Beta Round #66 9
243 Divisibility Rules Codeforces Codeforces Round #116 (Div. 2, ACM-ICPC Rules) 9
244 Present for Vitalik the Philatelist Codeforces Codeforces Round #325 (Div. 1) 9
245 Mister B and Astronomers Codeforces Codeforces Round #421 (Div. 1) 10
246 Number of Binominal Coefficients Codeforces Codeforces Round #323 (Div. 1) 10
247 Mister B and Beacons on Field Codeforces Codeforces Round #421 (Div. 1) & Codeforces Round #421 (Div. 2) 10
248 Prime factorization Codeforces VK Cup 2012 Wild-card Round 1 10
249 New Year Running Codeforces Good Bye 2014 10
250 Nephren Runs a Cinema Codeforces Codeforces Round #449 (Div. 1) 10
251 Jzzhu and Squares Codeforces Codeforces Round #257 (Div. 1) 10