作业 3 应用分支与循环结构解决问题

    

/*计算分段函数*/
#include<stdio.h>
int main(void)
{
    double x,y;
    printf("Enter x:");
    scanf("%lf",&x);
    if(x<0){
        y=-1;
    }
    else if(x=0){
        y=0;
    }
    else{
        y=1;
    }
    printf("y=%.0f
",y);
    return 0;
}

/*输入一个正整数 n，再输入 n 个学生的成绩，计算平均成绩，并统计所有及格学生的人数*/
#include<stdio.h>
int main(void)
{
    int count,i,n;     /*count记录及格人数*/
    double grade,total;        /*分别存放成绩，成绩之和*/
    printf("Enter n:");
    scanf("%d",&n);
    total=0;
    count=0;
    for(i=1;i<=n;i++){
        printf("Enter grade#%d:",i);
        scanf("%lf",&grade);
        total=total+grade;    /*累加成绩*/
        if(grade>=60){
            count++;
        }
    }
    
    printf("grade average=%.2f
",total/n);
    printf("Number of not failures=%d
",count);
    return 0;
}

/*统计英文字母、空格或回车、数字字符和其他字符*/
#include<stdio.h>
int main(void)
{
    int blank,letter,digit,other;
    char ch;      /*定义一个字符变量ch*/
    int i; 
    blank=letter=digit=other=0;   /*置存放统计结果的三个变量的初值为零*/
    printf("Enter 15 characters:");
    for(i=1;i<=15;i++){       /*循环执行10次*/
        ch=getchar();       /*从键盘输入一个字符，赋值给变量ch*/
        if((ch>='a'&&ch<='z')||(ch>='A'&&ch<='Z'))
            letter++;
        else if(ch>='0'&&ch<='9')
            digit++;
        else if(ch>=' '&&ch<=' ')
            blank++;
        else
            other++;
    }
    printf("blank=%d,letter=%d,digit=%d,other=%d
",blank,letter,digit,other);
    return 0;
}

/*判断该年是否为闰年*/
#include<stdio.h>
int main(void)
{
    int year,i,n;
    printf("enter n:");
    scanf("%d",&n);
    for(i=1;i<=n;i++){
        printf("enter year:");
            scanf("%d",&year);
            if(year=-1)
                break;
            if((year%4==0&&year%100!=0)||(year%400==0)){
                printf("YES,YES!!!!N");
            }
            else{
                    printf("NO,,NO,,NO
");
            }
    }
    return 0;
}

     

#include<stdio.h>
int main(void)
{
    char ch;      /*定义一个字符变量ch*/
    printf("chengjishi:");
    ch=getchar();      /*从键盘输入一个字符，赋值给变量ch*/
     switch(ch){    
  case 'A':
    printf("90-100
");
     break;     /*跳出switch语句*/
  case 'B':
    printf("80-89
"); 
     break;
  case 'C':
     printf("70-79
");
     break;
  case 'D':
     printf("60-69
");
     break;
  case 'E':
     printf("0-59
");
     break;
  default:
     printf("cuowu
");
    break;
    }
    return 0;
}    

/*查询自动售货机中商品的价格*/
#include<stdio.h>
int main(void)
{
    int choice,i;
    double price;
    for(i=1;i<=5;i++){
        printf("[1]select apples
");   /*查询苹果的价格*/
        printf("[2]select pears
");
        printf("[3]select oranges
");
        printf("[4]select grapes
");
        printf("[0]select Exit
");    /*退出查询*/
        printf("Enter choice:");
        scanf("%d",&choice);
        if(choice==0)
            break；    /*此处用break跳出for循环*/
switch(choice){
        case 1:price=3.00;break;
            case 2:price=2.50;break;
                case 3:price=4.10;break;
                    case 4:price=10.20;break;
                    default:price=0.00;break;
        }
        printf("price=%0.2f
",price);
    }
    return 0;

}