1．编写一个程序。该程序读取输入直到遇到#字符，然后报告读取的空格数目、读取的换行符数目以及读取的所有其他字符数目。
#include<stdio.h> #include<ctype.h> int main(void){ char ch; int count1,count2,count3; count1 = count2 = count3 = 0;
printf("Enter text to be analyzed(#to terminate)：n"); while((ch = getchar()) != '#'){ if ( ch == 'n'){ count1++; } else if(isspace(ch)){ count2++; } else if (!isspace(ch)){ count3++; } } printf("换行数量%d,空格数量%d,其他字符数量%d",count1,count2,count3); return 0; }
2．编写一个程序。该程序读取输入直到遇到#字符。使程序打印每个输入的字符以及它的十进制ASCII 码。每行打印8 个字符/编码对。建议：利用字符计数和模运算符(%)在每8 个循环周期时打印一个换行符。
#include<stdio.h> #define STOP '#' int main(void){ char ch; int length = 1; printf("Enter text to be analyzed(#to terminate)：n"); while((ch = getchar()) != STOP){ if(length%8==0){ printf("n"); } printf("%c/%d ",ch,ch); length++; } return 0; }
3．编写一个程序。该程序读取整数，直到输入0。输入终止后，程序应该报告输入的偶数(不包括0)总个数、偶数的平均值，输入的奇数总个数以及奇数的平均值。
#include<stdio.h> int main(void){ int num,even_num,odd_num; double even_count,odd_count;//必需定义为double类型,否则打印平均值会出错 even_num = odd_num = 0; even_count = odd_count = 0.0 ; printf("Enter int to be analyzed(0 to terminate)：n"); while (scanf("%d", &num) == 1 && num != 0){ if (num%2 == 0){ even_num++; even_count +=num; } else { odd_num++; odd_count +=num; } } if (even_count > 0) printf("Even have %d, even average is %.2fn",even_num,even_count / even_num); if (odd_num > 0) printf("Odd have %d,odd average is %.2f",odd_num,odd_count/odd_num); return 0; }
4．利用if else 语句编写程序读取输入，直到#。用一个感叹号代替每个句号，将原有的每个感叹号用两个感叹号代替，最后报告进行了多少次替代。
#include<stdio.h> #define STOP '#' int main(void){ char ch; int i; i = 0; while((ch = getchar()) != STOP){ if (ch == '.'){ putchar('!'); i++; } else if (ch == '!'){ putchar(ch); putchar(ch); i++; } else { putchar(ch); } } printf("n"); printf("count %d",i); return 0; }
5．用switch 重做练习3。
#include<stdio.h> int main(void){ int num,even_num,odd_num; double even_count,odd_count;//必需定义为double类型,否则打印平均值会出错 even_num = odd_num = 0; even_count = odd_count = 0.0 ; printf("Enter int to be analyzed(0 to terminate)：n"); while (scanf("%d", &num) == 1 && num != 0){ switch (num%2){ case 0: even_num++; even_count +=num; break; case 1: odd_num++; odd_count +=num; break; } } if (even_count > 0) printf("Even have %d, even average is %.2fn",even_num,even_count / even_num); if (odd_num > 0) printf("Odd have %d,odd average is %.2f",odd_num,odd_count/odd_num); return 0; }
6．编写一个程序读取输入，直到#，并报告序列ei 出现的次数。说明此程序必须要记住前一个字符和当前的字符。用诸如“Receive your eieio award.”的输入测试它。
#include<stdio.h> #define STOP '#' #define PREV_CHAR 'e' #define CURRENT_CHAR 'i' int main(void){ char ch, prev_char; int i; i = 0; prev_char = 0; printf("Enter text to be analyzed(#to terminate)：n"); while((ch = getchar()) != STOP){ if (ch == PREV_CHAR){ prev_char = ch; } if (ch == CURRENT_CHAR && prev_char == PREV_CHAR){ i++; } } printf("Enter of 'ei' %d ",i); return 0; }
7．编写程序，要求输入一周中的工作小时数，然后打印工资总额、税金以及净工资。作如下假设：
a．基本工资等级=10.00 美元/小时
b．加班(超过40 小时)=1.5 倍的时间
c．税率前300 美元为15%
下一个150 美元为20%余下的为25%。
用#define 定义常量，不必关心本例是否符合当前的税法。
#include<stdio.h> #define BASE 10.00 #define TAX_LEVEL1 300 #define TAX_LEVEL2 150 #define TAX_LEVEL1_RATE 0.15 #define TAX_LEVEL2_RATE 0.2 #define TAX_LEVEL3_RATE 0.25 #define BASE_HOUR 40 #define OVER_RATE 1.5 int main(void){ float num,wage,tax,real_wage,temp,real_hour; wage = tax = real_wage = real_hour = 0.0; printf("Please enter the number of hours you work a week：n"); scanf("%f",&num); if (num > BASE_HOUR){ real_hour = num + (num - BASE_HOUR)*OVER_RATE; } else { real_hour = num; } wage = real_hour*BASE; temp = wage - TAX_LEVEL1; if (temp <= 0){ tax += wage*TAX_LEVEL1_RATE; } else { tax +=TAX_LEVEL1*TAX_LEVEL1_RATE; if (temp<= TAX_LEVEL2){ tax += temp*TAX_LEVEL2_RATE; } else { tax += TAX_LEVEL2*TAX_LEVEL2_RATE; tax += (temp - TAX_LEVEL2) * TAX_LEVEL3_RATE; } } real_wage = wage - tax; printf("hour:%.2f wage:%.2f tax:%.2f real wage :%.2f",num,real_hour,wage,tax,real_wage); return 0; }
8．修改练习7 中的假设a，使程序提供一个选择工资等级的菜单。用switch 选择工资等级。程序运行的开头应该像这样：
*****************************************************************
Enter the number corresponding to the desired pay rate or action：
1)$8.75/hr 2)$9.33/hr
3)$10.00/hr 4)$11.20/hr
5)quit
*****************************************************************
如果选择1 到4，那么程序应该请求输入工作小时数。程序应该一直循环运行，直到输入5。如果输入1 到5 以外的选项，那么程序应该提醒用户合适的选项是哪些，然后再循环。用#define 为各种工资等级和税率定义常量。
#include<stdio.h> #define LEVEL1 8.75 #define LEVEL2 9.33 #define LEVEL3 10.00 #define LEVEL4 11.20 #define TAX_LEVEL1 300 #define TAX_LEVEL2 150 #define TAX_LEVEL1_RATE 0.15 #define TAX_LEVEL2_RATE 0.2 #define TAX_LEVEL3_RATE 0.25 #define BASE_HOUR 40 #define OVER_RATE 1.5 int main(void){ int level; float fee,num,wage,tax,real_wage,temp,real_hour; wage = tax = real_wage = real_hour = fee = 0.0; printf("*****************************************************************n"); printf("Enter the number corresponding to the desired pay rate or action：n"); printf("1)$8.75/hr 2)$9.33/hrn"); printf("3)$10.00/hr 4)$11.20/hrn"); printf("5)quitn"); printf("*****************************************************************n"); while(scanf("%d",&level) == 1 && level != 5){ switch(level){ case 1: fee = LEVEL1; break; case 2: fee = LEVEL2; break; case 3: fee = LEVEL3; break; case 4: fee = LEVEL4; break; default: printf("You should enter the number between 1 to 4 (5 to quit).n"); printf("Please enter the right number: n"); continue; } printf("Please enter the number of hours you work a week：n"); scanf("%f",&num); if (num > BASE_HOUR){ real_hour = num + (num - BASE_HOUR)*OVER_RATE; } else { real_hour = num; } wage = real_hour*fee; temp = wage - TAX_LEVEL1; if (temp <= 0){ tax += wage*TAX_LEVEL1_RATE; } else { tax +=TAX_LEVEL1*TAX_LEVEL1_RATE; if (temp<= TAX_LEVEL2){ tax += temp*TAX_LEVEL2_RATE; } else { tax += TAX_LEVEL2*TAX_LEVEL2_RATE; tax += (temp - TAX_LEVEL2) * TAX_LEVEL3_RATE; } } real_wage = wage - tax; printf("hour:%.2f wage:%.2f tax:%.2f real wage :%.2fn",real_hour,wage,tax,real_wage); printf("Please enter next number:n"); } printf("exit!"); return 0; }
没有学透getchar和scanf的区别，一开始用getchar获取输入，结果出错了。这也告诉自己，对学习要有敬畏之心，看都教材不是看小说，要了解的是细节不是大概，马虎不得。
9．编写一个程序，接受一个整数输入，然后显示所有小于或等于该数的素数。
#include<stdio.h> #include<stdbool.h> int main(void){ int num,i,k; bool isPrime; printf("Enter int number:n"); scanf("%d",&num); for(i=2;i<=num;i++){ for(k=2,isPrime = true;(k*k)<=i;k++){ if (i%k==0){ isPrime = false; } } if (isPrime){ printf("%lu ",i); } } return 0; }
10．1988 年United States Federal Tax Schedule 是近期最基本的。它分为4 类，每类有两个等级。下面是其摘要；美元数为应征税的收入。
| 种类 | 税金 |
| 单身 | 前17，850 美元按15%，超出部分按28% |
| 户主 | 前23，900 美元按15%，超出部分按28% |
| 已婚，共有 | 前29，750 美元按15%，超出部分按28% |
| 已婚，离异 | 前14，875 美元按15%，超出部分按28% |
例如，有20 000 美元应征税收入的单身雇佣劳动者应缴税金0.15×17 850 美元+0.28×(20 000美元–17 850 美元)。编写一个程序，让用户指定税金种类和应征税收入，然后计算税金。使用循环以便用户可以多次输入。
#include<stdio.h> #define TYPE1 1 #define TYPE2 2 #define TYPE3 3 #define TYPE4 4 #define TAX_RATE1 0.15 #define TAX_RATE2 0.28 #define TYPE1_BASE 17850 #define TYPE2_BASE 23900 #define TYPE3_BASE 29750 #define TYPE4_BASE 14875 int main(void){ double tax,income,base; int type; printf("请选择税金种类:n"); printf("1)单身 2)户主 3)已婚，共有 4)已婚，离异 5)退出n"); while(scanf("%d",&type) == 1 && type != 5){ switch(type){ case TYPE1: base = TYPE1_BASE; break; case TYPE2: base = TYPE2_BASE; break; case TYPE3: base = TYPE3_BASE; break; case TYPE4: base = TYPE4_BASE; break; default: printf("请输入1到4之间的数字，或者输入5为退出n"); continue; } printf("请输入您的应征税收入：n"); scanf("%lf",&income); if(income>base){ tax = base*TAX_RATE1+(income-base)*TAX_RATE2; } else { tax = income*TAX_RATE1; } printf("您共要缴纳%.2lf美元税金n",tax); printf("请输入您税金种类代码：n"); } printf("Exit."); return 0; }
感觉和第七、八题一样，而且更没有难度。
11．ABC Mail Order Grocery 朝鲜蓟的售价是1.25 美元/磅，甜菜的售价是0.65 美元/磅，胡萝卜的售价是0.89 美元/磅。在添加运输费用之前，他们为100 美元的订单提供5%的打折优惠。对5磅或以下的定单收取3.50 美元的运输和装卸费用；超过5 磅而不足20 磅的定单收取10.00 美元的运输和装卸费用；20 磅或以上的运输，在8 美元基础上每磅加收0.1 美元。编写程序，在循环中使用switch 语句，以便对输入a 的响应是让用户输入所需的朝鲜蓟磅数，b 为甜菜的磅数，c 为胡萝卜的磅数，而q 允许用户退出订购过程。然后程序计算总费用、折扣和运输费用(如果有运输费的话)，以及总数。随后程序应该显示所有的购买信息：每磅的费用、订购的磅数、该订单每种蔬菜的费用、订单的总费用、折扣，如果有的话加上运输费用，以及所有费用的总数。
#include<stdio.h> #define ARTICHOKE 'a' #define BEET 'b' #define CARROT 'c' #define ARTICHOKE_PRICE 1.25 #define BEET_PRICE 0.65 #define CARROT_PRICE 0.89 #define SHIP_FEE_LEVEL1 3.5 #define SHIP_FEE_LEVEL2 10.00 #define SHIP_FEE_LEVEL3 0.1 #define SHIP_FEE_LEVEL3_BASE 8.0 #define WEIGHT_LEVEL1 5 #define WEIGHT_LEVEL2 20 #define DISCOUNT 0.05 #define DISCOUNT_BASE 100 int main(void){ double fee_count,ship_fee,price,order_count,discount_count, pound_count,pound,artichoke_pound,beet_pound,carrot_pound,artichoke_fee,beet_fee,carrot_fee; char type; pound_count = discount_count = fee_count = ship_fee = order_count = artichoke_pound = beet_pound = carrot_pound = 0.0; artichoke_fee = beet_fee = carrot_fee = 0.0; printf("请选择要订购的蔬菜:n"); printf("a)朝鲜蓟 b)甜菜 c)胡萝卜 q)退出n"); while(scanf("%c",&type) == 1 && type != 'q'){ if( type != ARTICHOKE && type != BEET && type != CARROT ){ printf("请选择输入a到c之间的字母，或者输入q退出:n"); continue; } printf("您输入你要订购的磅数："); scanf("%lf",£); pound_count += pound; switch(type){ case ARTICHOKE: artichoke_pound = pound; artichoke_fee = pound*ARTICHOKE_PRICE; break; case BEET: beet_pound = pound; beet_fee = pound*BEET_PRICE; break; case CARROT: carrot_pound = pound; carrot_fee = pound*CARROT_PRICE; break; } } if (pound_count <= WEIGHT_LEVEL1){ ship_fee = SHIP_FEE_LEVEL1; } else if(pound_count > WEIGHT_LEVEL1 && pound_count < WEIGHT_LEVEL2){ ship_fee = SHIP_FEE_LEVEL2; } else { ship_fee = SHIP_FEE_LEVEL3_BASE+ (pound_count*0.1); } fee_count = ship_fee+artichoke_fee+beet_fee+carrot_fee; if (fee_count>DISCOUNT_BASE){ discount_count = DISCOUNT_BASE*DISCOUNT; } order_count = fee_count-discount_count+ship_fee; printf("你共订购了%.2f磅蔬菜，平均每磅%.2f美元 n",pound_count,order_count/pound_count); if (artichoke_fee>0){ printf("订购了朝鲜蓟%.2f磅 共%.2f美元n",artichoke_pound,artichoke_fee); } if (beet_fee>0){ printf("订购了甜菜%.2f磅 共%.2f美元n",beet_pound,beet_fee); } if (carrot_fee>0){ printf("订购了胡萝卜%.2f磅 共%.2f美元n",carrot_pound,carrot_fee); } printf("共%.2f美元 折扣优惠%.2f n",fee_count,discount_count); if (ship_fee>0){ printf("运费共%.2f n",ship_fee); } printf("订单金额%.2fn",order_count); return 0; }
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