ACM杯比赛往年试题集锦Word文档下载推荐.docx
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ACM杯比赛往年试题集锦Word文档下载推荐.docx
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1376
Accepted:
266
Description
Thenotoriousringleaderandcyber-criminalDerekWu,betterknownasDr.WhoHow,hasbeenconvictedformultipleabductionsandcyber-fraudsseveralminutesago.Hewillsoonbetransferredfromthecourttotheprisontoservealifesentence.IntelligencefromundercoverofficersinDr.WhoHow’soutlawedgangindicatesapossibleforciblerescueoperationbygangmembersinthecasethatDr.WhoHowisconvicted.Toensureasuccessfulescort,besidesadoptingenhancedsecuritymeasures,thepoliceforcefurtherdesirestominimizetheescorttime—thetimethatthemotorcadeofescorthastospendbetweendeparturefromthecourtandarrivalattheprison.
Thecomplextrafficconditioninthecityimposescomplicationsonthepoliceforce’sescorteffort.Whilethemunicipalgovernmenthasagreedtotemporarilyshutdownafewroadsforexclusivepoliceuse,theshut-downtimewindowsvaryamongroadsandaregenerallynarrowtoavoidexcessivelydisturbingthelifeofthecitizens.Themotorcadeofescortmustpassthroughanyroadentirelywithinitsshut-downtimewindowandnotuseanyroadthatthemunicipalgovernmenthasnotagreedtoshutdown.
Giveninformationaboutallroadsavailabletothepoliceforcefortheescort,determinetheshortestescorttime.
Input
Theinputcontainsasingletestcase.Thefirstlinecontainsfourintegersn,m,sandt(2≤n≤100;
0≤m≤1000;
1≤s,t≤n;
s≠t).Therearenjunctions,somepairsofwhichareconnectedbymroads.Thecourtandtheprisonarelocatedatthes-thandthet-thjunctions,respectively.Thenextmlineseachcontainfiveintegersx,y,b,eandc(1≤x,y≤n;
0≤b<
e≤104;
1≤c≤104),indicatingthatthedirectedlanesrunningfromthex-thjunctiontothey-thjunctionofaroadthattakesthemotorcadeofescortcunitsoftimetopassthroughwillbeshutdownbetweentimebande.Theearliesttimewhenthemotorcadecanleavethecourtistime0.
Output
Iftheescortispossible,printtheshortestescorttime;
otherwise,print“Impossible”.
SampleInput
4514
12011
12012
13132
24341
34341
SampleOutput
3
Hint
ThesampleisdepictedinFigure1.Eachjunctionisrepresentedbyanumberedspot.Eachroadisrepresentedbyanarrowlabeledwith
itsshut-downtimewindowandpass-throughtime.
Figure1:
Depictionofthesample
Thesecondroadlistedinthesampleisvirtuallyunusableforittakesthemotorcadeofescortlongertimetopassthroughthanitcanstayavailable.Theremainingfourroadsenablethefollowingtwoescortroutes:
1.
2.
(Thelabel
overanarrowindicatesthatthemotorcadepassesthroughthecorrespondingroadbetweentimesandt.)Thefirstroutetakesfourunitsofescorttime,whereasthesecondtakesthree,whichistheshortestpossible.
Source
PKUCampus2008(POJFounderMonthlyContest–2008.05.10),frkstyc
FullSteinerTopologies
1000MS
441
187
SpecialJudge
AfullSteinertopologyforagivenpointsetP={p1,p2,…,pn}isanundirectedtreeT=(V,E)whereV={v1,v2,…,vn,vn+1,…,v2n−2}isthesetofvertices,andEisthesetofedges.ThendistinctlylabeledleavesofT,v1,v2,…,vn,correspondtop1,p2,…,pn,respectively;
theremainingn−2vertices,vn+1,vn+2,…,v2n−2,calledtheSteinervertices,aremutuallyindistinguishableandeachhaveadegreeofthree.Figure2showstheonlyfullSteinertopologyforP={p1,p2,p3}.Figure3showsallthreedifferentfullSteinertopologiesforP={p1,p2,p3,p4}.
Figure2:
FullSteinertopologyforP={p1,p2,p3}
Figure3:
FullSteinertopologiesforP={p1,p2,p3,p4}
Givenn,thecardinalityofP,computethenumberofdistinctfullSteinertopologies.
Theinputcontainsmultipletestcases.Eachtestcaseconsistsofasingleintegern(3≤n≤107)onaseparateline.TheinputendswhereEOFismet.
Foreachtestcase,printtheansweronaseparateline.Youshallprinttheanswerroundedtofoursignificantdigits.Letm·
10ebethescientificformoftheroundedanswer,youshallprint“mEe”,givingallfoursignificantdigitsofmandstrippinganyleadingzeroesbeforee.
30
300
3000
30000
300000
3000000
1.000E0
8.687E36
5.677E697
1.462E10024
1.983E130306
4.215E1603145
7.937E19031556
IlluminatedPlanet
198
45
Aspaceprobeisonamissiontoobserveaplanetarysystem.Itisinstructedtoshootimagesofaplanet,whichorbitsastar,usingitso
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