双语版c++ 第四章答案.doc

Chapter Four Selection and Iteration Exercises1. Rewrite the following if-else using a switch statement:if ( marriage_status = S )cout single ;else if ( marriage_status = M )cout married ;else if ( marriage_status = W )cout widowed ;else if ( marriage_status = E )cout separated ;else if ( marriage_status = D )cout divorced ;elsecout error: invalid code ;解答：switch (marriage_status)case S:cout single ;break;case M: cout married ;break;case W: cout widowed ;break;case E: cout separated ;break;case D:cout divorced ;break;default:cout error: invalid code ;2. The following program segment displays an appropriate message depending on the values of three integers: n1, n2, and n3.if ( n1= n2 )if (n1 = n3 )cout n1, n2 and n3 have the same value endl ;elsecout n1 and n2 have the same value endl ;else if ( n1 = n3 )cout n1 and n3 have the same value endl ;else if ( n2 = n3 )cout n2 and n3 have the same value endl ;elsecout n1, n2 and n3 have different values endl ;Use spaces to improve the readability of this code.To test the various branches in this code you will need to construct five sets of test data, each set testing one of the branches. Construct the five sets of test data for n1, n2, and n3.解答：/*测试用例为：1 1 1 ，1 1 2 ，1 2 1 ，1 2 2 ，1 2 3*/#includeusing namespace std;int main()int n1,n2,n3;cinn1n2n3;if(n1=n2)if(n1=n3)coutn1,n2 and n3 have the same valueendl;elsecoutn1 and n2 have the same valueendl;else if(n1=n3)coutn1 and n3 have the same valueendl; else if(n2=n3)coutn2 and n3 have the same valueendl; elsecoutn1,n2 and n3 have the different valueendl;return 0;3. Write a program to read in two integers and check if the first integer is evenly divisible by the second. (Hint: use the modulus operator %.)解答：#includeusing namespace std;int main()int n1,n2;coutn1n2;if(n1%n2=0)coutn1 is evenly divisible by n2endl;else coutn1 is not evenly divisible by n2endl;return 0;4. Input two numbers and find the smaller of the two using the conditional operator ?:.解答：#includeusing namespace std;int main()int n1,n2;int smaller;coutn1n2;if(n1!=n2)smaller=(n1n2)?n1:n2;coutthe smaller one is smallerendl;elsecoutn1=n2endl;return 0;5. In a triangle, the sum of any two sides must be greater than the third side. （triangle：三角形）Write a program to input three numbers and determine if they form a valid triangle.解答：#includeusing namespace std;int main()double a ,b ,c;coutabc;if(a+b)c)&(a+c)b)&(c+b)a)coutthe three number can form a valid triangle.endl;return 0;coutthe three number can not form a valid triangle.endl;return 0;6. Input a persons height in centimetres and weight in kilograms and display a message indicating that they are either underweight, overweight or normal weight. As an approximation, a person is underweight if their weight is less than their height divided by 2.5 and they are overweight if their weight is greater than their height divided by 2.3.解答：#includeusing namespace std;int main()double height,weight;coutheightweight;if(weightheight/2.5)coutunderweight!endl;else if(weightheight/2.3)coutnormal weight!endl; elsecoutoverweightendl;return 0;7. Write a program that reads a single numeral from the keyboard and displays its value as a word. For example, an input of 5 will display the word five.解答：#includeusing namespace std;int main()int num;coutnum;switch(num)case 0:coutzeroendl; break;case 1:coutoneendl; break;case 2:couttwoendl; break;case 3:coutthreeendl; break;case 4:coutfourendl; break;case 5:coutfiveendl; break;case 6:coutsixendl; break;case 7:coutsevenendl; break;case 8:couteightendl; break;case 9:coutnineendl; break;default: coutplease input a single numberalendl;return 0;8. Write a program to input a number 1 to 7 from the keyboard, where 1 represents Sunday, 2 Monday, 3 Tuesday, etc. Display the day of the week corresponding to the number typed by the user. If the user types a number outside the range 1 to 7, display an error message.解答：#includeusing namespace std;int main()int theday;cintheday;int flag=1;while(flag)switch(theday)case 1:coutsundayendl; flag=0; break;case 2:coutmondayendl;flag=0;break;case 3:couttuesdayendl;flag=0;break;case 4:coutwednesdayendl;flag=0;break;case 5:coutthursdayendl;flag=0;break;case 6:coutfridayendl;flag=0;break;case 7:coutsaturdayendl;flag=0;break;default: couttheday;return 0;9. Add the increment operator (I or i) and the decrement operator (D or d) to the simple calculator program P4D.解答：#includeusing namespace std;int main()double a,b;double result;char opt;coutplease input like :1 i 3 or 1 d 3 aoptb;if(opt=i|opt=I)result=a+b;else if(opt=d|opt=D)result=a-b;else coutinput error!endl;coutthe result is result;return 0;10. Write a program to input the time of day in Ireland and display the equivalent time in Washington (- 5 hours), Moscow (+ 3 hours), and Beijing (+ 8 hours). Input the time in the 24-hour format, e.g. 22:35 (11:35 p.m.).解答：#includeint main()int hour,minute;int h;printf(please input the time of day in Ireland in 24-hour format );scanf(%d:%d,&hour,&minute);if(hour=0&hour=0&minute=59)if(h=hour-5)0) h+=24;printf(the equivalent time in Washington is %d:%d ,in Moscow is %d:%d ,in Beijing is %d:%d .,h,minute,(hour+3)%24,minute,(hour+8)%24,minute);else printf(error input!);return 0;11. Write a program to display the effects of an earthquake based on the Richter scale value: Richter scale value EffectsLess than 4 Little.4.0 to 4.9 Windows shake.5.0 to 5.9 Walls crack; poorly built buildings are damaged.6.0 to 6.9 Chimneys tumble; ordinary buildings are damaged.7.0 to 7.9 Underground pipes break; well-built buildings are damaged.More than 7.9 Ground rises and falls in waves; most buildings are destroyed.（Richter scale value：里氏震级）解答：#includeint main()float rsvalue;cinrsvalue;if(rsvalue0)int value=rsvalue;switch(value)case 1:;case 2:;case 3:coutLittle effects!endl;break; case 4:coutWindows shake!endl;break;case 5:coutWalls crack;poorly built buidings are damaged!endl;break;case 6:coutChimneys tumble;ordinary buidings are damaged!endl;break;case 7:coutUnderground pipes break;well-buildings are damaged!endl;break;default:coutGround rises and falls in waves;most buildings are destroyed!endl;break;elsecouterror input! 0 ; i /= 2, j+ )cout i j ;解答：输出：10152231413. Modify program P4F to calculate the average along with the total of the numbers entered.解答：#includeusing namespace std;int main()double a,b;double result;char opt;int num=0;double sum=0;double ave=0.0;while(1)coutplease input like :1 i 3 or 1 d 3 aoptb;num+=2;sum+=(a+b);if(opt=i|opt=I)result=a+b;else if(opt=d|opt=D)result=a-b;else coutinput error!endl;ave=sum/num;coutthe result is resultendl;coutthe average along with the total of the numbers entered is aveendl;return 0;14. Rewrite the following using a for i = 0, total = 0 ;while ( i n ;total += n ;i+ ;解答：#includeint main()int i=0,total=0;int n;loop:cinn; total+=n; i+; if(i10) goto loop;couttotal;return 0;15. What is displayed when the following program is run and the number 1234 is entered?int num ;cout num ;docout num % 10 ;num /= 10 ;while ( num != 0 ) ;解答：当输入为1234时，输出为432116. The following program segment is intended to compute 0.1 + 0.2 + 0.3 . + 99.8 + 99.9. It contains a flaw. What is it, and how would you correct it?float sum = 0.0 ;float i = 0.1 ;while ( i != 100.0 )sum += i ;i += 0.1 ;解答：#includeint main()double sum=0.0;double i=0.1;int j=1;while(j=999)sum+=i;i+=0.1;j+;coutsum;return 0;17. What is the output from the following?(a)for (int i = 0 ; i 5 ; i+ )for ( int j = i ; j 5 ; j+ )cout i j endl ;(b)for ( int i = 0 ; i 5 ; i+ )for ( int j = 0 ; j 5-i ; j+ )cout i j endl ;解答：（a）输出为：00，01，02，03，04，11，12，13，14，22，23，24，33，34，44（b）输出为：00,01,02,03,04,10,11,12,13,20,21,22,30,31,4018. Write a for loop to(a) display the numbers 0, 5, 10, 15, ., 100(b) display the numbers 1, 2, 4, 8, 16, ., 1024.解答：（a）#includeint main()for(int i=0;i=100;i+=5)couti,;return 0;（b）#includeint main()int sum=1;for(int i=1;i=11;i+)coutsum,; sum*=2;return 0;19. Write a program to find the sum of all the odd integers in the range 1 to 99.解答：#include#includeint main()int sum=0;for(int i=1;i=99;i+=2)sum+=i;coutsum;return 0;20. Write a program that outputs all the numbers from 5 and 50 that are divisible by 3 or 5.解答：#include#includeint main()for(int i=5;i=50;i+)if(i%3=0|i%5=0)coutiendl;return 0;21. Write a program to display all the hour and