| 501 | Cmmp | | ad-hoc | N/A |
| 502 | Cntgcd | Mihai Calancea | ONI 2013, Baraj | N/A |
| 503 | Cntlex | Tamio-Vesa Nakajima | Science On 2021, clasa 7-8 | N/A |
| 504 | Cntnk | Bogdan Ioan Popa, Daniel Popa | IIOT 2021-22 Runda 2 | N/A |
| 505 | Cntper | Eugenie Daniel Posdarascu | Algoritmiada 2014, Runda Finala |      2/5 |
| 506 | Cntsubsirmax | Tamio-Vesa Nakajima | InfoPro, Runda 2, Grupa A | N/A |
| 507 | Coach | Radu Berinde | ONI 2004 |      4/5 |
| 508 | Coarde în cerc | Tudor Muresan | utcn-2021 | N/A |
| 509 | Cobai | Horatiu Cristurean | info-arena 1.0 |      2/5 |
| 510 | Cochilie | Zoltan Szabo | OJSEPI 2021, clasa a 9-a | N/A |
| 511 | Coco Chanel | Eugenie Daniel Posdarascu | ad-hoc |      1/5 |
| 512 | Cod | Rodica Pintea | Lista lui Francu | N/A |
| 513 | Cod2 | Doru Popescu Anastasiu | Lot Juniori 2008 - Baraj 3 | N/A |
| 514 | Codificare | Dan Constantin Spatarel | Tabăra ICHB 2012, Ziua 1, Grupa 1 | N/A |
| 515 | Coduri | Roxana Tamplaru | ONI 2007, clasa 9 | N/A |
| 516 | Coduri Huffman | Arhiva Educationala | Arhiva Educationala | N/A |
| 517 | Coins | Adrian Vladu | Concurs de incalzire 2004 |      3/5 |
| 518 | Colaj | Carmen Minca | OJI 2008, clasa a 10-a | N/A |
| 519 | Colectie | Cosmin Silvestru Negruseri, Leonard Crestez | Finala GInfo 2005 |      4/5 |
| 520 | Colete | Chichirim George | Concursul National de Informatica "Adolescent Grigore Moisil" 17 | N/A |
| 521 | Colier | Cosmin Gheorghe | Algoritmiada 2009, Runda 2 | N/A |
| 522 | Coliziuni | Teodor Plop | Algoritmiada 2015 Runda Finala | N/A |
| 523 | Collar | Andrei Heidelbacher | Algoritmiada 2014, Runda 2 | N/A |
| 524 | Colonii | Florin Pop | ACM ICPC Faza Nationala 2015 | N/A |
| 525 | Color | Mugurel Ionut Andreica | Lot 2002 |      4/5 |
| 526 | Color 4 | Ionut Bogdanescu | ad-hoc | N/A |
| 527 | Color2 | Mugurel Ionut Andreica | ONI 2004 |      3/5 |
| 528 | Color3 | Mircea Bogdan Pasoi | Lot Bistrita 2009, Baraj 1 | N/A |
| 529 | Color5 | Din Folclor | Lot Deva 2013 - Baraj 2 Seniori | N/A |
| 530 | Colorare | Cosmin Silvestru Negruseri | Bursele Agora 2006 |      4/5 |
| 531 | Colorare2 | Cosmin Silvestru Negruseri | Algoritmus, runda 4 |      5/5 |
| 532 | Colorare3 | Bogdan-Cristian Tataroiu | Stelele Informaticii 2010 | N/A |
| 533 | Colorfulconflict | Mihai Calancea, Tamio-Vesa Nakajima | Algoritmiada 2019 Runda PreONI | N/A |
| 534 | Colors | Cristina Sichim | ProSoft@NT 2017 | N/A |
| 535 | Colors2 | Costin Oncescu | RMI 2018 | N/A |
| 536 | Combinari | Arhiva Educationala | ad-hoc | N/A |
| 537 | Combl | Cosmin Gheorghe | Infoarena Cup 2014 | N/A |
| 538 | Comentariu | Mihai Calancea | ONIS 2015, Runda Finala | N/A |
| 539 | Comisia | Adrian Budau, Andrei Popa | Algoritmiada 2016 Runda 3 Seniori | N/A |
| 540 | Comitat | Rodica Pintea | ONI 2002, clasele 11-12 | N/A |
| 541 | Comoara | Marius Andrei | Lot Alba Iulia 2004 | N/A |
| 542 | Comoditate | Mihai Calancea | ONIS 2015, Runda 2 | N/A |
| 543 | Comp2 | Mugurel Ionut Andreica | preONI 2002 | N/A |
| 544 | Compact | Filip Cristian Buruiana | Algoritmiada 2010, Runda 4 | N/A |
| 545 | Compact2 | Mihai Calancea | Algoritmiada 2015 Runda Finala | N/A |
| 546 | Compact3 | Alex Tatomir | ONI 2019, clasele 11-12, ziua 2 | N/A |
| 547 | Compania | Mugurel Ionut Andreica | BOI 2003 |      4/5 |
| 548 | Competition | Alexandru Petrescu | Tuymaada 2019 | N/A |
| 549 | Complet | Adrian Panaete | Lot Vaslui 2014 Seniori Baraj 6 | N/A |
| 550 | Componente biconexe | Arhiva Educationala | Arhiva educationala | N/A |