《硬件趣学Python编程》 07 loop

Lecture7

LoopsCProgrammingLanguageOutlinewhileLoopsdo-whileLoopsforLoopsLoopsControlNestedLoopsAlgorithmPatternsgotoLoopsLoopsarewidelyusedtodealwithrepeatedworkwithspecificpatterns.Threetypesofloopswhiledo-whileforwhileLoopssyntax

while(exp)statement;Example1,2NYexpistrue?statementwhileLoopsBeforewritingaloopstructure,thinkabouthowmanytimedoyouwanttorepeat?howtostarttheloop?howtoendit?And…DonotmaketheloopendlessDonotrepeattheloopstatementonetimemore,oronetimelessdo-whileLoopssyntax

dostatement;while(exp);Example1’,2’NYstatementexpistrue？forLoopssyntax

for(exp1;exp2;exp3)statement;

Example1’’,2’’NYexp1

statementexp3exp2istrue?forLoopspleasenotethethreeexpressionswithintheforstatementcanbeomitted.Butthesemicolonsmustremain.for(;n<=100;n++)for(;n<=100;)for(;;)Practicewriteaprogramtocalculatethefactorialofanintegerx,whichisinputtedbyusers.LoopsControlbreak;andcontinue;statementscanbeusedtochangetheflowofloops.break; exitloopdirectly.continue; stoprunningtheremainstatementsofaloopandstartnextround.willchecktheloopconditionasnormalwillrunexp3inforloops

LoopsControlfor(i=1;i<5;i++){if(i%2==0)break;printf(“i=%d\n”,i);}for(i=1;i<5;i++){if(i%2==0)continue;printf(“i=%d\n”,i);}ThinkAbout...writeaprogramtoasktheusertoinputanintegerx,checkifxisaprimenumberornot.EndlessLoopsfor(;;)isaendlessloop,likewhile(1)Sometimesendlessloopsareuseful,butyoumustendtheloopproperly.Example2’’’NestedLoopsThestatementofaloopisanotherloopstructure.Therearetwo-layerloops,three-layerloops,orloopswithmorelayers.NestedLoopsHowtocalculate1!+2!+3!+…+10!NestedLoopsAnotherwaytocalculate1!+2!+3!+…+10!Donotusenestedloop.NestedLoopsHowtofindallprimenumbersbetween100and200?NestedLoopsWhatelsecannestedloopsdo?Example3,4AlgorithmPatternsOuterloopInnerloopSelection(flowcontrol)gotoandlabelsCprovidesgotostatementtojumpoff,andlabelstobranchto.if…goto…structureisabletoaccomplishaloopstructure.usinggotoisnotrecommended.Example5Question?Suggestion?HomeworkPage8