C-chap05-Repetition

Chapter5RepetitionSchoolofInformationEngineering,NanchangHangkongUniversity1Chapter5RepetitionChapter5RepetitionSchoolofInformationEngineering,NanchangHangkongUniversity2ObjectivesBasicLoopStructuresThewhileStatementComputingSumsandAveragesUsingawhileLoopTheforStatementCaseStudies:LoopProgrammingTechniquesNestedLoopsThedo-whileStatementCommonProgrammingandCompilerErrorsChapter5RepetitionSchoolofInformationEngineering,NanchangHangkongUniversity3KeypointsBasicLoopStructuresThewhileStatementTheforStatementChapter5RepetitionSchoolofInformationEngineering,NanchangHangkongUniversity4IntroductionAsectionofcodethatisrepeatediscalledaloop（循环）,becauseafterthelaststatementinthecodeisexecuted,theprogrambranches,orloops,backtothefirststatementandstartsanotherrepetitionthroughthecodeEachrepetitionisalsocalledaniteration（迭代）orpassthroughtheloop（通过循环）Chapter5RepetitionSchoolofInformationEngineering,NanchangHangkongUniversity5BasicLoopStructuresConstructingarepeatingsectionofcoderequiresthatfourelementsbepresent:Repetitionstatement（循环语句）whilestatementforstatementdo-whilestatementCondition（条件）Astatementthatinitiallysetstheconditionbeingtested（设置被测条件式初始值的语句）Astatementwithintherepeatingsectionofcodethataltersthecondition（改变条件式的语句）sothatiteventuallybecomesfalseChapter5RepetitionSchoolofInformationEngineering,NanchangHangkongUniversity6PretestandPosttestLoopspretestloop（前测试循环）Chapter5RepetitionSchoolofInformationEngineering,NanchangHangkongUniversity7PretestandPosttestLoopsposttestloop（后测试循环）Chapter5RepetitionSchoolofInformationEngineering,NanchangHangkongUniversity8Counter-ControlledandCondition-ControlledLoopsCounter-controlledloop（计数器控制循环）:theconditionisusedtokeeptrackofthenumberofrepetitionsAlsoknownasafixed-countloop（固定计数循环）Condition-controlledloop（条件控制循环）:thetestedconditiondoesnotdependonacountbeingachieved,butratheronaspecificvaluebeingencounteredChapter5RepetitionSchoolofInformationEngineering,NanchangHangkongUniversity9BasicLoopStructuresChapter5RepetitionSchoolofInformationEngineering,NanchangHangkongUniversity10ThewhileStatementThegeneralformofthewhilestatementiswhile(expression)statement;Thetransferofcontrolbacktothestartofawhilestatementtoreevaluatetheexpressionisknownasaprogramloop（程序循环）Thefollowingisavalidbutinfiniteloop:while(count=10)printf(%d,count);Chapter5RepetitionSchoolofInformationEngineering,NanchangHangkongUniversity11ThewhileStatementChapter5RepetitionSchoolofInformationEngineering,NanchangHangkongUniversity12ThewhileStatementOutputis:12345678910Chapter5RepetitionSchoolofInformationEngineering,NanchangHangkongUniversity13ThewhileStatementOutputis:10987654321Chapter5RepetitionSchoolofInformationEngineering,NanchangHangkongUniversity14ThewhileStatementOutputis:NUMBERSQUARECUBE----------------111248392741664525125636216749343864512981729101001000Chapter5RepetitionSchoolofInformationEngineering,NanchangHangkongUniversity15Condition-controlledloopOutputis:DEGREESDEGREESCELSIUSFAHRENHEIT-----------------541.001050.001559.002068.002577.003086.003595.0040104.0045113.0050122.00ThewhileStatementChapter5RepetitionSchoolofInformationEngineering,NanchangHangkongUniversity16Example-Fibonacci1,1,2,3,5,8,13,21,34,55,…Noticethatweonlyneedtwoelementsinordertocalculatethenextone.11+112+11211231123+1123511235+11235811235811235813112358131123581321ThewhileStatementChapter5RepetitionSchoolofInformationEngineering,NanchangHangkongUniversity17intfib1=1,fib2=1,fib_next=0;printf(%d,fib1);while(fib2lim){printf(%d,fib2);fib_next=fib1+fib2;fib1=fib2;fib2=fib_next;}printf(\n);Screen8lim1fib11fib20fib_nextThewhileStatementChapter5RepetitionSchoolofInformationEngineering,NanchangHangkongUniversity18intfib1=1,fib2=1,fib_next=0;printf(%d,fib1);while(fib2lim){printf(%d,fib2);fib_next=fib1+fib2;fib1=fib2;fib2=fib_next;}printf(\n);1Screen8lim1fib11fib20fib_nextThewhileStatementChapter5RepetitionSchoolofInformationEngineering,NanchangHangkongUniversity19intfib1=1,fib2=1,fib_next=0;printf(%d,fib1);while(fib2lim){printf(%d,fib2);fib_next=fib1+fib2;fib1=fib2;fib2=fib_next;}printf(\n);1Screen8lim1fib11fib20fib_nextThewhileStatementChapter5RepetitionSchoolofInformationEngineering,NanchangHangkongUniversity20intfib1=1,fib2=1,fib_next=0;printf(%d,fib1);while(fib2lim){printf(%d,fib2);fib_next=fib1+fib2;fib1=fib2;fib2=fib_next;}printf(\n);11Screen8lim1fib11fib20fib_nextThewhileStatementChapter5RepetitionSchoolofInformationEngineering,NanchangHangkongUniversity21intfib1=1,fib2=1,fib_next=0;printf(%d,fib1);while(fib2lim){printf(%d,fib2);fib_next=fib1+fib2;fib1=fib2;fib2=fib_next;}printf(\n);11Screen8lim1fib11fib22fib_nextThewhileStatementChapter5RepetitionSchoolofInformationEngineering,NanchangHangkongUniversity22intfib1=1,fib2=1,fib_next=0;printf(%d,fib1);while(fib2lim){printf(%d,fib2);fib_next=fib1+fib2;fib1=fib2;fib2=fib_next;}printf(\n);11Screen8lim1fib11fib22fib_nextThewhileStatementChapter5RepetitionSchoolofInformationEngineering,NanchangHangkongUniversity23intfib1=1,fib2=1,fib_next=0;printf(%d,fib1);while(