第四章 選擇_管理學_高等教育_教育專區(qū).docx

第四章 選擇所有的演算法(Algorithm)都可以用循序(sequential),選擇(selection)以及重複(repetition)三類流程完整描述4.1 Algorithms描述方式l 1.Pseudocode(虛擬程式碼)-較常用 以口語化的方式描述執(zhí)行步驟 Example:(以sequential structure描述) 將兩個數(shù)值存入電腦,存成x和y兩個變數(shù) 將x和y相加,相加後除以2,存入變數(shù)Average 將Average輸出l 2.流程圖(常用流程圖符號請參考表4.1(p.4-4) start輸入x,y計算Average輸出結(jié)束 P.S課本(4-3.3flowchart)有詳細流程圖page4-4(表4-1)有符號名稱介紹l 3.程式碼(以c+描述) int average; int x,y; cinxy; average=(x+y)/2 cout The average value of x and yis0 x=y y0)b.字元比次序(大小):因為char以1byte之整數(shù)儲存 AC E=C 範例程式1 /CharInput.cpp #include using std:cin; using std:cout; int main() char ch; coutPlease input a character(y or n): ch; if(ch=Y|ch=y) coutYou input a yes endl; else coutYou input a no endl;注意:=不可寫成=(assignment operator)會變成將(Y或y)(N或n)指派給chl 2. if statement(省略else) if(條件式)statement 1(加練習題1)l 3. Nested if-else statements 將if-else結(jié)構(gòu)置入if and else之間 for example if(條件1) if(條件2)statement1elsestatement2else statement3範例程式2假設(shè)方程式為,當時,根為,當,根為試寫一程式,判斷方程式之根為實數(shù)或複數(shù),並求其解/Root2.cpp#include using std:cin; using std:cout; using std:endl; int main() double a,b,c,D;coutPlease input a: a; coutPlease input b:b; coutPlease input c:c; if(a=0) if(b=0) coutNo answerendl; else coutOnly one solution- c/bendl;else D=b*b- 4.0*a*c; if(D=0) coutDouble same roots:-b/(2.0*a)0.0) coutTwo real rootsendl; coutFirst root:(-b+sqrt(0)/(2.0*a)endl; coutSecond root:(-b-sqrt(0)/(2.0*a)endl;else coutTwo wnjutic endl; coutFirst root:(-b)/(2.0*a)+isqrt(-D)/(2.0*a)endl; coutSecond root: (-b)/(2.0*a)-isqrt(-D)/(2.0*a)endl;return 0;範例程式3(進階題)試寫一程式，經(jīng)由輸入三角形三邊長，判斷是否可以形成三角形，若可以則計算各內(nèi)角角度。(資料不足時可自行假設(shè))#include using std:cin;using std:cout;using std:endl;#include #include using std:setprecision;int main()double a,b,c;double h;double C1,C2,C3; double max;coutabc; if ( (a+b)c & (b+c)a & (c+a)b )cout These three lengths can form a triangle max)max = a;if ( b max)max = b;h = pow(a+b+c)*(a+b-c)*(a-b+c)*(b+c-a),0.5)/(2*b);cout The height is hendl;C1=asin(h/max)*180/3.14;C2=180-asin(h/a)*180/3.14;C3=(180-C1-C2);cout The angle of tirangle is setprecision(5)C1C, C2C and C3C;else cout These three lengths cannot form a triangleendl;return 0;練習1:寫一個程式,經(jīng)由輸入兩個整數(shù),判斷第一個數(shù)字是否為第二個數(shù)字的倍數(shù)練習2:寫一程式,要求使用者輸入座標(X,Y),判斷其象限l 4. If-else chain(較為簡易可讀) if(條件1) statement1 else if(條件2) statement2 else if(條件3) statement3 else statement4範例程式1Write a program that reads in five integers and determines and prints the largest and the smallest integers in the group./ 本程式寫法有很多種，限於只能用if指令，故程式較長，且故意將寫法與同學不同#include using std:cin;using std:cout;using std:endl;int main()int a,b,c,d,e;int max;int min;couta;max = a;min = a;coutb;if ( b max)max = b;else if (b min)min = b;coutc;if ( c max)max = c;else if (c min)min = c;coutd;if ( d max)max = d;else if (d min)min = d;coute;if ( e max)max = e;else if (e min)min = e;cout nMaximum value is max;cout nMinimum value is minendl;return 0;範例程式2綜合所得稅所得淨額稅率累進差額 /Tax.cpp #include using std:cin; using std:cout; using std:endl; int main() float Income,Tax; double a=0.06,b=0.13,c=0.21,d=0.3,e=0.4; coutPlease input Net Income:Income; if(Income0.0) coutYou input a minus income!endl; else if(Income330000.0) Tax=Income * a; else if(Income890000.0) Tax=Income * b-23100; else if(Income1780000.0) Tax=Income * c-94300; else if(Income3340000.0) Tax=Income * d-254500; else Tax =Income * e-588500; coutYou must payt Taxt to governmentendl; return 0; 範例程式3假設(shè)便利商店工讀生月薪依下列公式計算：060hr，75元/小時；6175hr，以1.2倍計算；76小時以後以1.75倍計算。試撰寫一程式，程式中輸入工讀生該月工作時數(shù)，計算實領(lǐng)薪水。#include using std:cout;using std:cin;using std:endl;int main()int WH;double Salary;cout WH;if (WH=60)Salary = 75*WH;else if (WH 75)Salary = 75*(60+15*1.2+double(WH-75)*1.75);cout You can earn $ Salary N.T.n;return 0;範例程式4將學生依下列分類方式分級。059：E； 6069：D； 7079：C； 8089：B； 90100：A；試撰寫一程式，程式中輸入學生成績，印出其分數(shù)所屬等級。#include using std:cout;using std:cin;using std:endl;int main()int exam;cout exam;if (exam60)coutEn;else if (exam 70)coutDn;else if (exam 80)coutCn;else if (exam 90)coutBn;else if (exam = 100)coutAn;return 0;4.3 Switch敘述語法switch(整數(shù)表達式) case 值1: statement 1 break; case 值2: statement 2 break; default: statement 3範例程式1.Seasons.cpp依使用者輸入月份判斷該月份所屬季節(jié)/Seasons.cpp#includeusing std:cin;using std:cout;using std:endl;int main() int month; coutn Please input a month:month;if(month1|month12) coutYou input a wrong month!nendl;else coutmonthmonth is; switch(month%12)/3) case 0: coutWinterendl; break; case 1:coutSpringendl; break; case 2:coutSummerendl; break; case 3:coutAutumnendl; break; default:coutYou never arrival here!endl;return 0;範例程式2寫一個程式,讀入學生成績等級(有A or aB or bC or cD or d),當輸入A時,印出Excellent!,B時,印出Good!,C時,印出Be study hard!,其他則印出Failed!#include using std:cin;using std:cout;using std:endl;int main()char grade;coutgrade;switch(grade)case A: case a:coutExcellentendl;break;case B: case b:coutGoodendl;break;case C: case c:coutbe study hardendl;break;case D: case d:coutFailedendl;break;default:coutYou input a wrong characterendl;return 0;範例程式3.說明char也可以比對大小,且字母的ASCII值介於65和122之間本程式檢查使用者輸入的字母是子音還是母音 /CharTest.cpp #include using std:cin; using std:cout; using std:endl; int main() char c; coutn Please input a character:c; if(c122) coutYour input is not a char!; else coutThe char you input is; switch(c) case a: case e: case i:case o:case u:case A:case E:case I:case O:case U:cout母音字母endl;break;default: cout子音字母endl;return 0;範例程式4以Switch撰寫程式：將學生成績依下列方式分級。(059：E)、(6069：D)、(7079：C)、(8089：B)、(90100：A)，輸入分數(shù)時，自動告知其等級。#include using std:cin;using std:cout;using std:endl;int main()int exam;coutexam;if (exam 100 | exam 0)cout You input a wrong value.endl;elseswitch(exam/10)case 0: case 1: case 2: case 3: case 4: case 5:coutEendl;break;case 6:coutDendl;break;case 7: coutCendl;break;case 8:coutBendl;break;case 9:cout Aendl;break;default:coutProgram never arriveendl;return 0;範例程式5請用Switch 指令撰寫停車場收費系統(tǒng)：已知收費停車場小客車收費20元/hr，大客車收費50元/hr，機車10元/hr，腳踏車5元/hr，不足一小時以一小時計算，不足10分鐘不算費用，請設(shè)計一個收費系統(tǒng)，能輸入車種及停車時數(shù)，自動判斷應收費用。#include using std:cin;using std:cout;using std:endl;#include int main()int kind;double time;int itime,pay;cout please input the kind of carn 1 for car, 2 for bus, 3 for motorcycle, 4 for bicyclekind;if ( (kind=1) & (kind =4)cout please input parking hours:time;if (int(time*60)%60 10)itime = floor(time);elseitime = ceil(time);switch(kind)case 1: pay = itime*20;break;case 2:pay = itime*50;break;case 3:pay = itime*10;break;case 4:pay = itime*5;break;default:cout The program never arrive here. endl;cout You must pay pay dollars.endl; else cout Your input cannot regonize.endl;return 0;範例程式6試用switch語法撰寫一程式，計算大明是否被列入明道管理學院期中預警名單之中，已知計算方式為(A)期中前小考三次平均得x，占60%。(B)作業(yè)成績有兩次得h，占40%。(C)加分紀錄a，額外計算。(D)扣分紀錄m，額外計算。故期中成績x計算公式如下：輸入大明各項成績，總成績小於60分時，列入預警名單，低於70分時，列入觀察名單。高於90分時，列入優(yōu)秀名單。#include using std:cin;using std:cout;using std:endl;#include int main()double t1,t2,t3;double h1,h2;double a;double m;double y;int judge; coutPlease input the test record with 3 timest1t2t3;cout Pplease input homework record with 2 timesh1h2;cout Please input the add recorda;cout Please input the minus recordm;y = (t1+t2+t3)/3*0.6+(h1+h2)/2*0.4+a-m;judge = int(y/10);switch(judge)case 0: case 1: case 2: case 3: case 4: case 5: coutYou must study very hard.endl; break;case 6: coutYou must study hard.endl; break;case 9: case 10: coutYou are very good student.endl; break;default: coutYou are good student.endl;return 0;4.4 條件運算子(Conditional Operator)語法:條件式 ? 表達式1 : 表達式2說明:當條件式的值為true,選擇表達式1,否則選擇表達式2Example:1.if(ab) coutab; else cout=b;可寫成(ab)?(a=b);Example:2.if(ab) c=a; else c=b; 可寫成c=(ab) ? a : b);範例程式1.Condition.cpp可判斷兩個數(shù)值何者較大,及奇偶數(shù) /Condition.cpp #include using std:cin; using std:cout; using std:endl; int main() float a,b; int N; cout(1)Please input two numbers:a; cinb; coutThe bigger one between a and b is b? a : b )endl; cout(2)Please input a integer N:N; coutN is(N%2?odd:even)endl; return 0;範例程式2.試撰寫一程式，輸入三個整數(shù)，找出最大及最小值，並計算三數(shù)之平均值。注意，平均值可能有小數(shù)點。#include using std:cout;using std:cin;using std:endl;int main()int A,B,C;int max,min;double average;cout A;cinB;cinC; max = ( (C (AB?A:B)?C:(AB?A:B) );min = ( (C (AB?A:B)?C:(AB?A:B) ); average = double(A+B+C)/3;cout nMaximum value is max;cout nMinimum value is min;cout nAverage value is average;return 0;練習題.買東西時，輸入所應付款金額及實際交給店員金額，輸出則為應找回最少的鈔票數(shù)與錢幣數(shù)。例如買了一個東西33元，給店員1000元，應找回967元，其中有500元一張、100元四張、 50元硬幣一個、十元硬幣一個、五元硬幣一個及一元硬幣一個。l *第四章作業(yè)l *1. Write a program that reads in five integers and determines and prints the largest and the smallest integers in the group.2. Write a program that reads in the radius of a circle and prints the circles diameter, circumferences and area.3. Writes a program that inputs three integers from the keyboard and prints the sum, average, product, smallest and largest of these numbers.4. Write a program that calculates the squares and cubes of the numbers from 0 to 10 and uses tabs to print the following tables of values:Number square cube0 0 01 1 12 4 83 9 27.10 100 10005. Write a program that inputs a five-digit number, separates the number into its individual digits and prints the digits separated from one another by three spaces each.6. Write a program that reads in two integers and determines and prints if the first is a multiple of the second.7. Suppose the students can pass the exam if his grade is greater than 60. Write a program that can input the students grade and determine whether he can pass the exams. 8. 已知兩點可以決定一條線性函數(shù)，試寫一程式，經(jīng)由輸入兩點座標即可計算及之值。9. 已知二次方程式，試寫一程式，經(jīng)由輸入、及求算其根。10. 試寫一程式，經(jīng)由輸入三角形三邊長，判斷是否可以形成三角形，若可以則計算各內(nèi)角角度。(資料不足時可自行假