小宝的第三章1

#include<stdio.h>
int main(void)
{
    int choice,i;
    double price;

    for(i=1;i<=5;i++){

        printf("[1]Select crisps
");
        printf("[2]Select popcorn
");
        printf("[3]Select chocolate
");
        printf("[4]Select cola
");
        printf("[0]exit
");

        printf("Enter choice:");
        scanf("%d",&choice);

        if(choice==0)
            break;

        switch(choice){
            case 1:price=3.0;break;
            case 2:price=2.5;break;
            case 3:price=4.0;break;
            case 4:price=3.5;break;
            default:price=0.0;break;
        }

        printf("price=%0.1f
",price);
    }
    printf("Thanks
");

    return 0;
}

#include<stdio.h>
int main(void)
{
    int digit,letter,other;
    char ch;
    int i;
    digit=letter=other=0;
    printf("Enter 10 characters:");
    for(i=1;i<=10;i++){
        ch=getchar();
        if((ch>='a'&&ch<='z')||(ch>='A'&&ch<='Z'))
            letter++;
        else if(ch>='0'&&ch<='9')
            digit++;
        else
            other++;
    }
    printf("letter=%d,digit=%d,other=%d
",letter,digit,other);

    return 0;
}

#include<stdio.h>
int main(void)
{
    double valuel,value2;
    char op;
    printf("Type in an expression:");
    scanf("%lf%c%lf",&valuel,&op,&value2);

    if(op=='+')
        printf("=%.2f
",valuel+value2);
    else if(op=='-')
        printf("=%.2f
",valuel-value2);
    else if(op=='*')
        printf("=%.2f
",valuel*value2);
    else if(op=='/')
        printf("=%.2f
",valuel/value2);
    else
        printf("Unknown operator
");

    return 0;
}

#include<stdio.h>
int main(void)
{
    double x,y;

    printf("Enter x:");
    scanf_s("%lf",&x);
    if(x<0){
        y=0;
    }
    else if(x<=15){
        y=4*x/3;
    }
    else{
        y=2.5*x-10.5;
    }
    printf("f(%.2f)=%.2f
",x,y);

    return 0;
}

#include<stdio.h>
int main(void)
{
    int count,i,n;
    double grade,total;

    printf("Enter n:");
    scanf_s("%d",&n);
    total=0;
    count=0;
    for(i=1;i<=n;i++){
        printf("Enter grade#%d:",i);
        scanf_s("%lf",&grade);
        total=total+grade;
        if(grade<60){
            count++;
        }
    }
    printf("Grade average=%.2f
",total/n);
    printf("Number of failures=%d
",count);

    return 0;
}

/* 判断整数的奇偶性 */
#include<stdio.h>
int main(void)
{
    int number;

    printf("Enter a number:");
    scanf_s("%d",&number);
    if(number%2==0){
        printf("The number is even.
");
    }
    else{
        printf("The number is odd.
");
    }

    return 0;
}

/* 简单的猜数游戏 */
#include<stdio.h>
int main(void)
{
    int  mynumber=38;
    int  yournumber;

    printf("Input your number:");
    scanf_s("%d",&yournumber);
    if(yournumber==mynumber)
        printf("Ok!you are right!
");
    else
        if(yournumber>mynumber)
            printf("Sorry!your number is bigger than my number!
");
        else
            printf("Sorry!your number is smaller than my number!
");

    return 0;
}