实验三-简单的分支与循环结构

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

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

	for(i=1,i<=1,i++){
		printf("Enter x:");
		scanf("%if",&x);
		if(x<=0){
			printf("Error!");

		}

		else if(x<=50){
			y=0.53*x;
        }
			
		else(x>50){
			y=0.58*x;

		}
		printf("y=f(%f)=%.1.0f
,x,y);

	}
	return 0;

}





	

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

        y=0;
    }
    else{
        y=1;
        
    }
   printf("y=%d
",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,num; 
    double grade,total; 
    num=0;
    total=0;
    count=0;
    printf("Enter grade:
");
    scanf_s("%Lf",&grade);
    while(grade>=0){
        total=total+grade;
        num++;
        if(grade>=60)
            count++;
        scanf_s("%Lf",&grade);
    }
    if(num!=0){
        printf("Grade average is %.2f
",total/num);
        printf("The number of 及格的人 is %d
",count);
    }
    else
        printf("Grade average is 0
");
    return 0;
}
 

#include<stdio.h>
int main(void)
{
    int i,year,n;    
    printf("请输入n");
    scanf_s("%d",&n);
    printf("Input -1 to quit:");
    scanf_s("%d", &year);
if( year==-1 )
   return -1;
    for(i=1;i<=n;i++){
        printf("请输入年份：");
    scanf_s("%d",&year);
     if((year%4==0&&year%100!=0)||(year%400==0)){
        printf("这一年是闰年！
");
    }
    else{
        printf("这一年不是闰年！
");
    }
    }
    
    return 0;
    }

#include <stdio.h>
int main(void)
{
    char ch;
    printf("输入成绩：");
        ch=getchar();
    switch(ch){    
  case 'A':
                 printf("90-100
");
     break;
  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("Invalid input
");
    break;
    }
    return 0;
}