作业3

#include<stdio.h>
int main(void)
{
    int i,n,year;
    printf("Enter n:");
    scanf("%d",&n);
    for(i=1;i<=n;i++){
        printf("Enter year:");
        scanf("%d",&year);
        if((year%4==0&&year%100!=0)||(year%400==0)){
            printf("这是闰年");
        }
        else{
            printf("这不是闰年");
        }
    }
        return 0;

    }

#include<stdio.h>
int main()
{
    int x,y;
    printf("Enter x ");
    scanf("%d",&x);
    if(x<0){
        y=-1;
    }
    else if(x==0){
        y=0;
    }
    else{
        y=1;
    }
    printf("y=%d",y);
    
    return 0;
}
        

#include<stdio.h>
int main(void)
{
    int n,i,c;
    double g,total;
    printf("输入人数n ");
    scanf("%d",&n);

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

    return 0;
}
    

#include<stdio.h>
int main(void)
{
    int digit,letter,other;
    char ch;
    int i;
    digit=letter=other=0;
    printf("Enter 15 characters:");
    for(i=1;i<=15;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\n",letter,digit,other);

    return 0;
}

#include<stdio.h>
int main(void)
{
    char op;
    printf("输入五级制成绩:");
    scanf("%c",&op);
    switch(op){
        case'A':printf("grade=90-100");
            break;
        case'B':printf("grade=80-89");
            break;
        case'C':printf("grade=70-79");
            break;
        case'D':printf("grade=60-69");
            break;
        case'E':printf("grade=0-59");
            break;
    }
    return 0;
}

#include<stdio.h>
int main(void)
{
    int i,x;
    double price;
    
    for(i=1;i<=5;i++){
        printf("[1]apples\n");
        printf("[2]pears\n");
        printf("[3]oranges\n");
        printf("[4]grapes\n");
        printf("[0]exit\n");
        printf("输入编号：\n");
        scanf("%d",&x);
        if(x==0)
            break;
        switch(x){
            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=%.3f",price);
    }
    return 0;
}