/*计算分段函数*/
#include<stdio.h>
int main()
{float x=0,y=0;printf("请输入x：");scanf("%f",&x);if(x>0)y=1;else if(x==0)y=0;elsey=-1;printf("当x=%f时,y=%f\n",x,y);return 0;
}

#include<stdio.h>
int main(void)
{int count,i,n;double grade,total;printf("Enter n:");scanf("%d",&n);total=0;count=0;for(i=1;i<=n;i++){printf("Enter grade#%d:\n",i);scanf("lf",&grade);total=total+grade;if(grade>=60){count++;}}printf("Grade average=%.2f\n",total/n);printf("Number of failures=%d\n",count);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<=10;i++){ch=getchar();if((ch>='a'&&ch<='z')||(ch>='A'&&ch<='Z'))letter++;else if(ch>='0'&&ch<='14')digit++;elseother++;}printf("letter=%d,digit=%d,other=%d\n",letter,digit,other);return 0;
}

#include<stdio.h>
int main(void)
{int n,year;printf("Enter a year: ");scanf("%d",&year);for(year++)if(year%100==n){printf("-1\n");break;}if(year%100!=n && year%4=n && year%400=n)printf("%d 是闰年。\n",year);elseprintf("-1\n");return 0;
}

#include<stdio.h>
int main(void)
{int score;char level;printf("请输入成绩：\n");scanf("%d",&score);if(score<80)if(score<70)if(score<60)printf("E\n");elseprintf("D\n");elseprintf("C\n");elseif(score<90)printf("B\n");elseprintf("A\n");return 0;
}

#include<stdio.h>
int main(void)
{int choice,i;double price;for(i=1;i<=5;i++){printf("[1]Select apples\n");printf("[2]Select pears\n");printf("[3]Select oranges\n");printf("[4]Select grapes\n");printf("[0]Exit\n");printf("Enter choice: ");scanf("%d",&choice);if(choice==0)break;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\n",price);}printf("Thanks\n");return 0;
}