c语言的四道题目,明天补考...

Question

1.SUM=2+5+8+11+14·····,输入正整数n,求表达式的前n项和和SUM.
2.*****TIME*****
1 morning
2 afternoon
3 night
Please enter your choice:
屏幕上显示出如上表格,用户选择1时显示Good morning,选择2时显示 Good afternoon,选择3时显示Good night ,输入其他选择显示 Slelction error!.
3.编写程序,从键盘输入一个1到12的任意一个数,输出该数对应的月份共有的天数.如输入3,输出3月有31天.
4.已知有10个整数:12,36,72,36,36,99,87,12,35,36,编写程序,统计该10个数中36出现的次数,并输出他们的位置.(提示:用数组存放数据)

本人分数负43了，等有分数一定都加上...

Answer 1

1.
main()
{
int n,sum,i;
scanf("%d",n);
sum=2;
for(i=1;i<n;i++)
{
sum=sum+3
}
printf("%d\n",sum);
}
2.
main()
{
int c;
printf("*****TIME*****\n");
printf("1 morning\n");
printf("2 afternoon\n");
printf("3 night\n");
printf("please enter your choice:");
scanf("%d",c);
switch(c)
{
case 1:
printf("Good morning\n");
break;
case 2:
printf("Good afternoon\n");
break;
case 3:
printf("Good night\n");
break;
default:
printf("Selection error!\n");
break;
}
}
3.
main()
{
int n,x;
scanf("%d",n);
switch(n)
{
case 1:
case 3:
case 5:
case 7:
case 8:
case 10:
case 12:
x=31;break;
case 2:
x=28;break;
case 4:
case 6:
case 9:
case 11:
x=30;break;
default:
printf("Error\n");
}
printf("the month %d has %d days.\n",n,x);
}
4.
main()
{
int a[10]={12,36,72,36,36,99,87,12,35,36},b[10];
int i,n=0;
for(i=0;i<10;i++)
{
if(a[i]==36)
{n+=1;
printf("%d",i+1);
}
printf("the 36:%d",n);
}