C# solutions to the 200 most-solved problems on SPOJ: www.spoj.com/users/davidgalehouse/
Problems are ranked (roughly) by difficulty using the levels from Civ V, from Settler (easiest) to Deity (hardest).
| Date | Problem | Solution | Tags | Difficulty |
|---|---|---|---|---|
| 2015/04/28 | TEST | TEST.cs | #io | Settler |
| 2015/09/20 | PRIME1 | PRIME1.cs | #primes #sieve | King |
| 2015/12/28 | ADDREV | ADDREV.cs | #ad-hoc #digits | Chieftain |
| 2016/01/01 | ONP | ONP.cs | #parsing #recursion #stack #strings | Prince |
| 2016/01/05 | FCTRL | FCTRL.cs | #factorial #factors #math | King |
| 2016/06/04 | FCTRL2 | FCTRL2.cs | #big-numbers #factorial | Emperor |
| 2016/06/05 | SAMER08F | SAMER08F.cs | #ad-hoc #dynamic-programming-1d #math | King |
| 2016/06/05 | NSTEPS | NSTEPS.cs | #ad-hoc | Chieftain |
| 2016/06/07 | ACPC10A | ACPC10A.cs | #sequence | Warlord |
| 2016/06/08 | CANDY | CANDY.cs | #ad-hoc #division | Warlord |
| 2016/06/10 | FASHION | FASHION.cs | #ad-hoc #sorting | Prince |
| 2016/06/10 | TOANDFRO | TOANDFRO.cs | #ad-hoc #strings | Warlord |
| 2016/06/12 | AE00 | AE00.cs | #division #math | Prince |
| 2016/06/12 | LASTDIG | LASTDIG.cs | #digits #mod-math | King |
| 2016/06/16 | JULKA | JULKA.cs | #big-numbers #math | Emperor |
| 2016/06/19 | CANDY3 | CANDY3.cs | #division #mod-math | Warlord |
| 2016/06/19 | COINS | COINS.cs | #dynamic-programming-1d #recursion | King |
| 2016/06/25 | EIGHTS | EIGHTS.cs | #digits #math | Prince |
| 2016/06/26 | HANGOVER | HANGOVER.cs | #binary-search #sequence | Warlord |
| 2016/06/28 | PALIN | PALIN.cs | #ad-hoc | King |
| 2016/06/30 | ACODE | ACODE_v1.cs | #dynamic-programming #memoization #recursion | King |
| 2016/07/03 | WILLITST | WILLITST.cs | #game #math | Prince |
| 2016/07/03 | ABSYS | ABSYS.cs | #ad-hoc #strings | Warlord |
| 2016/07/04 | CANTON | CANTON.cs | #ad-hoc #math #sequence | King |
| 2016/07/05 | STAMPS | STAMPS.cs | #sorting | Warlord |
| 2016/07/06 | PERMUT2 | PERMUT2.cs | #ad-hoc #permutations | Prince |
| 2016/07/07 | ARMY | ARMY.cs | #ad-hoc | Chieftain |
| 2016/07/09 | TRICOUNT | TRICOUNT.cs | #math #proof | King |
| 2016/07/10 | AP2 | AP2.cs | #math #sequence | Prince |
| 2016/07/10 | FENCE1 | FENCE1.cs | #math | Warlord |
| 2016/07/10 | STPAR | STPAR.cs | #ad-hoc #greedy #stack | King |
| 2016/07/12 | PT07Y | PT07Y.cs | #graph-theory #tree | King |
| 2016/07/16 | GIRLSNBS | GIRLSNBS.cs | #division | Warlord |
| 2016/07/17 | NGM | NGM.cs | #game | King |
| 2016/07/17 | INVCNT | INVCNT.cs | #ad-hoc #bst | Emperor |
| 2016/07/21 | CRDS | CRDS.cs | #ad-hoc #sequence | Warlord |
| 2016/07/21 | EDIST | EDIST.cs | #dynamic-programming-2d #strings | Emperor |
| 2016/07/26 | BEENUMS | BEENUMS.cs | #formula #math #proof | King |
| 2016/08/02 | PT07Z | PT07Z.cs | #bfs #graph-theory #longest-path #proof #tree | Immortal |
| 2016/08/07 | AGGRCOW | AGGRCOW.cs | #binary-search #greedy #optimization | Emperor |
| 2016/08/08 | BISHOPS | BISHOPS.cs | #ad-hoc #math | Prince |
| 2016/08/08 | BYTESM2 | BYTESM2.cs | #dynamic-programming-2d #path-optimization | King |
| 2016/08/09 | OLOLO | OLOLO.cs | #binary #io | Emperor |
| 2016/08/09 | OFFSIDE | OFFSIDE.cs | #ad-hoc | Prince |
| 2016/08/10 | MAXLN | MAXLN.cs | #math #proof | King |
| 2016/08/11 | HPYNOS | HPYNOS.cs | #digits #simulation | Prince |
| 2016/08/11 | NY10A | NY10A.cs | #buckets #sorting #strings | Warlord |
| 2016/08/14 | LASTDIG2 | LASTDIG2.cs | #big-numbers #digits #mod-math | King |
| 2016/08/14 | HUBULLU | HUBULLU.cs | #game #proof | Emperor |
| 2016/08/15 | EASYPROB | EASYPROB.cs | #binary #recursion | Prince |
| 2016/08/15 | ARITH2 | ARITH2.cs | #ad-hoc #parsing #strings | Prince |
| 2016/08/21 | GSS1 | GSS1.cs | #divide-and-conquer #segment-tree | Immortal |
| 2016/09/05 | BITMAP | BITMAP.cs | #bfs | King |
| 2016/09/05 | PARTY | PARTY.cs | #dynamic-programming-2d #knapsack #optimization | King |
| 2016/09/07 | ETF | ETF.cs | #factors #formula #math #primes #sieve | Emperor |
| 2016/09/08 | MARBLES | MARBLES.cs | #big-numbers #combinatorics #math | King |
| 2016/09/09 | TRT | TRT_v1.cs | #memoization #optimization #recursion | Emperor |
| 2016/09/10 | EGYPIZZA | EGYPIZZA.cs | #ad-hoc #division | Prince |
| 2016/09/10 | AMR10G | AMR10G.cs | #sorting | King |
| 2016/09/11 | AIBOHP | AIBOHP.cs | #dynamic-programming-2d #optimization | Emperor |
| 2016/09/12 | FARIDA | FARIDA.cs | #dynamic-programming-1d | Prince |
| 2016/09/14 | ANARC09A | ANARC09A.cs | #greedy #recursion #stack | Emperor |
| 2016/09/17 | PIGBANK | PIGBANK_v1.cs | #dynamic-programming-1d #knapsack #optimization | King |
| 2016/09/17 | NHAY | NHAY.cs | #strings | Emperor |
| 2016/09/18 | MIXTURES | MIXTURES.cs | #dynamic-programming-2d #memoization #optimization | Emperor |
| 2016/09/19 | SBANK | SBANK.cs | #hash-table #radix-sort #sorting | Emperor |
| 2016/09/19 | JAVAC | JAVAC.cs | #ad-hoc #strings | Warlord |
| 2016/09/21 | QUADAREA | QUADAREA.cs | #formula | Chieftain |
| 2016/09/21 | HOTELS | HOTELS.cs | #greedy #optimization #sliding-window | King |
| 2016/09/22 | DOTAA | DOTAA.cs | #ad-hoc #division #game #io | Warlord |
| 2016/09/25 | HORRIBLE | HORRIBLE_v1.cs | #divide-and-conquer #lazy #segment-tree | Immortal |
| 2016/10/02 | BUGLIFE | BUGLIFE.cs | #dfs #graph-theory | Emperor |
| 2016/10/02 | FACEFRND | FACEFRND.cs | #ad-hoc #hash-table | Prince |
| 2016/10/02 | GUESSING | GUESSING.txt | #ad-hoc | Chieftain |
| 2016/10/02 | GCD2 | GCD2.cs | #big-numbers #gcd #math | Prince |
| 2016/10/03 | ARRAYSUB | ARRAYSUB.cs | #deque #sliding-window | Emperor |
| 2016/10/04 | GSS3 | GSS3.cs | #divide-and-conquer #segment-tree | Immortal |
| 2016/10/05 | TWOSQRS | TWOSQRS.cs | #factors #math #mod-math #primes #sieve | Emperor |
| 2016/10/06 | ANARC05B | ANARC05B.cs | #sequence #sorting | King |
| 2016/10/07 | TDPRIMES | TDPRIMES.cs | #primes #sieve | King |
| 2016/10/08 | ABCDEF | ABCDEF.cs | #ad-hoc #combinatorics #hash-table #math | Emperor |
| 2016/10/09 | MAJOR | MAJOR_v1.cs | #ad-hoc | King |
| 2016/10/09 | ACPC11B | ACPC11B.cs | #binary-search #merge #sorting | King |
| 2016/10/10 | PPATH | PPATH.cs | #graph-theory #primes #sieve | Emperor |
| 2016/10/11 | FIBOSUM | FIBOSUM.cs | #formula #math #memoization #mod-math #sequence | Emperor |
| 2016/10/12 | PIR | PIR.cs | #formula #math | Warlord |
| 2016/10/12 | ENIGMATH | ENIGMATH.cs | #gcd #math | Prince |
| 2016/10/14 | SILVER | SILVER.cs | #ad-hoc #binary #combinatorics #proof | Emperor |
| 2016/10/14 | COMDIV | COMDIV.cs | #division #factors #io #math #primes #sieve | Emperor |
| 2016/10/15 | AMR12D | AMR12D.cs | #ad-hoc #strings | Warlord |
| 2016/10/15 | GLJIVE | GLJIVE.cs | #ad-hoc #binary #sequence | Prince |
| 2016/10/15 | DANGER | DANGER.cs | #formula #game #math | Prince |
| 2016/10/16 | HISTOGRA | HISTOGRA.cs | #ad-hoc #optimization #sliding-window #stack | Immortal |
| 2016/10/16 | MCOINS | MCOINS.cs | #dynamic-programming #game | King |
| 2016/10/17 | ACPC10D | ACPC10D.cs | #dynamic-programming-2d #path-optimization | King |
| 2016/10/17 | ALICESIE | ALICESIE.cs | #division #sieve | Prince |
| 2016/10/18 | PHONELST | PHONELST.cs | #strings #trie | Emperor |
| 2016/10/19 | CPRMT | CPRMT.cs | #ad-hoc #buckets #strings | Prince |
| 2016/10/19 | MISERMAN | MISERMAN.cs | #dynamic-programming-2d #path-optimization | King |
| 2016/10/22 | DISUBSTR | DISUBSTR.cs | #sorting #strings #suffixes | Emperor |
| 2016/11/12 | BYECAKES | BYECAKES.cs | #ad-hoc #division #optimization | Warlord |
| 2016/11/12 | FAVDICE | FAVDICE.cs | #math #probability #proof | Emperor |
| 2016/11/12 | DIEHARD | DIEHARD.cs | #game #memoization | King |
| 2016/11/14 | DQUERY | DQUERY.cs | #bit #offline #sorting | Deity |
| 2016/11/16 | SUMITR | SUMITR.cs | #dynamic-programming-2d #golf #path-optimization | King |
| 2017/02/26 | CSTREET | CSTREET.cs | #graph-theory #greedy #heap #mst #prims | Immortal |
| 2018/04/10 | BUSYMAN | BUSYMAN.cs | #ad-hoc #greedy #sorting | King |
| 2018/07/08 | ABCPATH | ABCPATH.cs | #dag #dfs #greedy #memoization | King |
| 2018/07/08 | KGSS | KGSS.cs | #divide-and-conquer #segment-tree | Immortal |
| 2018/07/09 | HACKRNDM | HACKRNDM_v1.cs | #sliding-window #sorting | King |
| 2018/07/23 | SHPATH | SHPATH.cs | #dijkstras #graph-theory #greedy #heap #shortest-path | Immortal |
| 2018/07/26 | AMR11E | AMR11E.cs | #factors #math #primes #sieve | King |
| 2018/07/26 | SUMFOUR | SUMFOUR.cs | #ad-hoc #binary-search #combinatorics #hash-table | Emperor |
| 2018/07/27 | MUL | MUL.cs | #big-numbers | Chieftain |
| 2018/07/28 | BRCKTS | BRCKTS.cs | #divide-and-conquer #segment-tree | Immortal |
| 2018/07/29 | LABYR1 | LABYR1.cs | #bfs #graph-theory #longest-path #proof #tree | Immortal |
| 2018/07/30 | MICEMAZE | MICEMAZE.cs | #dijkstras #graph-theory #greedy #heap #shortest-path | Immortal |
| 2018/08/03 | LCA | LCA.cs | #divide-and-conquer #graph-theory #lca #segment-tree #stack #tree | Immortal |
| 2018/08/09 | INTEST | INTEST.cs | #io | Emperor |
| 2018/08/11 | INOUTEST | INOUTEST.cs | #io | Emperor |
| 2019/01/04 | QTREE | QTREE_v1.cs | #divide-and-conquer #graph-theory #hld #lca #segment-tree #tree | Deity |
| 2019/01/06 | CADYDIST | CADYDIST.cs | #ad-hoc #sorting | Warlord |
| 2019/01/06 | EC_CONB | EC_CONB.cs | #ad-hoc #binary | Warlord |
| 2019/01/07 | RPLC | RPLC.cs | #ad-hoc | Warlord |
| 2019/01/07 | CAM5 | CAM5.cs | #dfs #disjoint-sets | Emperor |
| 2019/01/09 | BOMARBLE | BOMARBLE.cs | #math | Warlord |
| 2019/01/10 | ABSP1 | ABSP1.cs | #ad-hoc #proof | Prince |
| 2019/01/11 | ROOTCIPH | ROOTCIPH.cs | #factors #formula #io #math | Immortal |
| 2019/01/13 | MRECAMAN | MRECAMAN.cs | #ad-hoc #memoization | Warlord |
| 2019/01/13 | UPDATEIT | UPDATEIT.cs | #bit | Immortal |
| 2019/01/13 | BYTESE2 | BYTESE2.cs | #ad-hoc #sorting | King |
| 2019/01/13 | TRGRID | TRGRID.cs | #ad-hoc #recursion | King |
| 2019/01/14 | JNEXT | JNEXT.cs | #ad-hoc #greedy #sorting | King |
| 2019/01/14 | NY10E | NY10E.cs | #dynamic-programming-2d | King |
| 2019/01/15 | ZSUM | ZSUM.cs | #ad-hoc #math #mod-math #sequence | King |
| 2019/01/16 | POUR1 | POUR1.cs | #ad-hoc #mod-math #simulation | Emperor |
| 2019/01/17 | NOTATRI | NOTATRI.cs | #binary-search #sliding-window #sorting | Emperor |
| 2019/01/18 | LENGFACT | LENGFACT.cs | #formula #math | Prince |
| 2019/01/18 | CRSCNTRY | CRSCNTRY.cs | #dynamic-programming-2d | King |
| 2019/01/19 | NAKANJ | NAKANJ.cs | #bfs | King |
| 2019/01/19 | PERMUT1 | PERMUT1.cs | #dynamic-programming-2d #permutations | Emperor |
| 2019/01/24 | ABA12C | ABA12C.cs | #dynamic-programming-2d #knapsack #optimization | Emperor |
| 2019/01/25 | TWENDS | TWENDS.cs | #dynamic-programming-2d #game #optimization | Emperor |
| 2019/01/26 | GAMES | GAMES.cs | #ad-hoc #gcd #proof | King |
| 2019/01/26 | CUBEFR | CUBEFR.cs | #sieve | Prince |
| 2019/01/26 | ALIEN | ALIEN.cs | #sliding-window | Emperor |
| 2019/01/27 | EKO | EKO.cs | #binary-search #sorting | Emperor |
| 2019/01/27 | ONEZERO | ONEZERO.cs | #ad-hoc #bfs #bitmask #mod-math | Emperor |
| 2019/01/27 | ASSIGN | ASSIGN.cs | #bitmask #dynamic-programming | Immortal |
| 2019/01/28 | CHOCOLA | CHOCOLA.cs | #ad-hoc #greedy #sorting | Emperor |
| 2019/01/29 | DSUBSEQ | DSUBSEQ.cs | #dynamic-programming #memoization #mod-math | Emperor |
| 2019/01/29 | TSHOW1 | TSHOW1.cs | #binary #math | King |
| 2019/01/30 | ATOMS | ATOMS.cs | #math | Warlord |
| 2019/01/30 | HIGHWAYS | HIGHWAYS.cs | #dijkstras #graph-theory #greedy #heap #shortest-path | Immortal |
| 2019/01/30 | PT07X | PT07X.cs | #graph-theory #greedy | Emperor |
| 2019/01/31 | MFLAR10 | MFLAR10.cs | #ad-hoc | Warlord |
| 2019/01/31 | CEQU | CEQU.cs | #formula #gcd #math | King |
| 2019/01/31 | EBOXES | EBOXES.cs | #math | Prince |
| 2019/02/01 | IITKWPCB | IITKWPCB.cs | #factors #math #proof | King |
| 2019/02/02 | BWIDOW | BWIDOW.cs | #ad-hoc | Warlord |
| 2019/02/02 | SCPC11B | SCPC11B.cs | #ad-hoc #sorting | Warlord |
| 2019/02/02 | ANARC09B | ANARC09B.cs | #gcd | Prince |
| 2019/02/02 | SPEED | SPEED.cs | #ad-hoc #gcd #math | Emperor |
| 2019/02/03 | UJ | UJ.cs | #big-numbers | Warlord |
| 2019/02/03 | WACHOVIA | WACHOVIA.cs | #dynamic-programming-2d #knapsack #optimization | King |
| 2019/02/03 | MAYA | MAYA.cs | #ad-hoc | Warlord |
| 2019/02/03 | STREETR | STREETR.cs | #ad-hoc #gcd | Prince |
| 2019/02/03 | WORDCNT | WORDCNT.cs | #ad-hoc | Warlord |
| 2019/02/03 | POLEVAL | POLEVAL.cs | #ad-hoc | Warlord |
| 2019/02/04 | RPLN | RPLN.cs | #divide-and-conquer #segment-tree | Immortal |
| 2019/02/04 | BLINNET | BLINNET.cs | #disjoint-sets #mst | Emperor |
| 2019/02/05 | SUBST1 | SUBST1.cs | #sorting #strings #suffixes | Emperor |
| 2019/02/05 | QTREE2 | QTREE2.cs | #divide-and-conquer #graph-theory #lca #segment-tree #tree | Immortal |
| 2019/02/06 | APS | APS.cs | #factors #primes #sieve | Emperor |
| 2019/02/06 | SHOP | SHOP.cs | #dijkstras #graph-theory #greedy #heap #shortest-path | Immortal |
| 2019/02/07 | ANARC08H | ANARC08H.cs | #formula #game | King |
| 2019/02/07 | CODESPTB | CODESPTB.cs | #bit #sorting | Immortal |
| 2019/02/08 | NEG2 | NEG2.cs | #ad-hoc #binary | Emperor |
| 2019/02/09 | CATM | CATM.cs | #bfs #simulation | King |
| 2019/02/09 | PON | PON.cs | #math #primes | Emperor |
| 2019/02/10 | SQRBR | SQRBR.cs | #dynamic-programming-2d | Emperor |
| 2019/02/10 | ROCK | ROCK.cs | #dynamic-programming-2d | Emperor |
| 2019/02/10 | IOIPALIN | IOIPALIN.cs | #dynamic-programming-2d #optimization | Emperor |
| 2019/02/10 | ELEVTRBL | ELEVTRBL.cs | #bfs | Prince |
| 2019/02/10 | ANARC05H | ANARC05H.cs | #dynamic-programming-2d | Emperor |
| 2019/02/11 | LITE | LITE.cs | #divide-and-conquer #lazy #segment-tree | Immortal |
| 2019/02/11 | SCUBADIV | SCUBADIV.cs | #memoization #recursion | Emperor |
| 2019/02/12 | FREQUENT | FREQUENT.cs | #divide-and-conquer #segment-tree | Immortal |
| 2019/02/12 | CPCRC1C | CPCRC1C.cs | #ad-hoc #digits | Emperor |
| 2019/02/13 | YODANESS | YODANESS.cs | #ad-hoc #bst | Emperor |
| 2019/02/13 | MATSUM | MATSUM.cs | #bit | Immortal |
| 2019/02/13 | PIE | PIE.cs | #binary-search #optimization | Emperor |
| 2019/02/13 | ALLIZWEL | ALLIZWEL.cs | #dfs #recursion | Emperor |
| 2019/02/14 | MULTQ3 | MULTQ3.cs | #divide-and-conquer #lazy #segment-tree | Deity |
| 2019/02/14 | M3TILE | M3TILE.cs | #ad-hoc #dynamic-programming #recursion | Emperor |
| 2019/02/14 | GNYR09F | GNYR09F.cs | #binary #dynamic-programming-3d | King |
| 2019/02/15 | BEADS | BEADS.cs | #ad-hoc #sorting | King |
| 2019/02/15 | CHICAGO | CHICAGO.cs | #dijkstras #graph-theory #greedy #heap #shortest-path | Immortal |
| 2019/02/15 | RENT | RENT.cs | #binary-search #dynamic-programming-1d #sorting | Emperor |
| 2019/02/16 | WORDS1 | WORDS1.cs | #euler-path #graph-theory | Immortal |
| 2019/02/16 | BABTWR | BABTWR.cs | #ad-hoc #dynamic-programming-1d | Emperor |
| 2019/02/17 | KQUERY | KQUERY.cs | #bit #offline #sorting | Immortal |
| 2019/02/18 | MKTHNUM | MKTHNUM.cs | #binary-search #divide-and-conquer #merge #segment-tree #sorting | Deity |
| 2019/07/14 | CMPLS | CMPLS.cs | #math #sequence | King |
| 2019/09/12 | ORDERSET | ORDERSET.cs | #binary-search #bit #compression #offline #sorting | Deity |
| 2020/03/04 | GERGOVIA | GERGOVIA.cs | #greedy | King |
Solutions are unit tested, which relies on compiling them from source programmatically using Roslyn. This is necessary because I want them to be submittable to SPOJ without modification or namespace clutter, so their build actions have to be set to none to prevent compilation errors like CS0101 and CS0017.
To keep everything clean, I/O is separated from the actual problem solving. Performance of .NET's number parsing and Console I/O can be an issue. I use them whenever possible, but custom I/O handling is sometimes necessary.
Reusable components are housed in the Spoj.Library project. Due to performance concerns I usually don't bother programming with extensibility or safety in mind.