task 1

#include<stdio.h>
#include<stdlib.h>
#include<time.h>
#define N 5

int main()
{
int grade, number;
int i;

srand(time(0));

for(i=0;i<N;++i)
{
grade=rand()%4+2018;
number=rand()%999+1;
printf("%d8330%04d\n",grade, number);
}

return 0; }

task 2

#include<stdio.h>
#include<stdlib.h>
#include<time.h>

#define N 3 /*猜測的次數*/

int main()
{ int lucky_day,guess_day,flag,i;

srand(time(0));
lucky_day=rand()%30+1;
flag=1;

printf("猜猜2022年4月哪一天會是你的Lucky day.\n\n開始嘍，你有%d次機會，猜吧(1~30): ",N);

for(i=N;i>0;i--)
{
scanf("%4d",&guess_day);
if(guess_day==lucky_day)
{
printf("\n哇，猜中了:-)\n");
flag=0;
break;
}
else if(guess_day!=lucky_day)
{
if(guess_day<lucky_day)
printf("\n你猜的日期早了，你的Lucky day還沒到呢\n\n");
else printf("\n你猜的日期晚了，你的Lucky day已經過啦\n\n");

if(i!=1) printf("再猜(1~30): ");
}
}

if(flag)
printf("\n次數用完啦，偷偷告訴你：4月，你的Lucky day是%d號",lucky_day);

return 0;
}

task 3

#include<stdio.h>

int main()
{
char a;
printf("請輸入交通訊號燈顏色（r表示red，g表示green，y表示yellow）：\n");
while(scanf("%s",&a)!=EOF)
{
switch(a)
{
case 'r':printf("stop!\n\n");break;
case 'g':printf("go go go\n\n");break;
case 'y':printf("wait a minute\n\n");break;
default:printf("something must be wrong...\n\n");
}
}
return 0;
}

task 4

#include<stdio.h>
#include<math.h>

int main()
{
int i,n,a,k;double s;
while(scanf("%d%d",&n,&a)!=EOF)
{
k=0;s=0;
for(i=1;i<=n;i++)
{
k=k*10+a;
s+=1.0*i/k;
}
printf("n=%d,a=%d,s=%f\n\n",n,a,s);
}
return 0;
}

task 5

#include<stdio.h>

int main()
{
int line[9]={1,2,3,4,5,6,7,8,9};
int row[9]={1,2,3,4,5,6,7,8,9};
int value;

int i,j;

for(i=0;i<9;i++)
{
for(j=0;j<=i;j++)
{
printf("%2d ×%2d = %-3d",row[j],line[i],row[j]*line[i]);
}

printf("\n");
}

return 0;
}

task6(1)

#include<stdio.h>

int main()
{
int n,i;
scanf("%d",&n);
printf("input n:%d\n",n);

for(i=1;i<=n;i++)
{
printf(" o \n");
printf("<H>\n");
printf("I I\n\n");
}
return 0;
}

task6(2)

#include<stdio.h>

int main()
{
int i,n;
scanf("%d",&n);
printf("input n:%d\n",n);

for(i=1;i<=n;i++)
{
printf(" o ");
}
printf("\n");
for(i=1;i<=n;i++)
{
printf("<H> ");
}
printf("\n");
for(i=1;i<=n;i++)
{
printf("I I ");
}
return 0;
}

task6(3)

#include<stdio.h>

int main()
{
int i,j,n;
printf("input n:");
scanf("%d",&n);
printf("\n");

for(i=1;i<=n;i++)
{
for(j=1;j<i;j++)
{
printf(" ");
}
for(j=1;j<=2*(n+1-i)-1;j++)
{
printf(" o ");
}
printf("\n");

for(j=1;j<i;j++)
{
printf(" ");
}
for(j=1;j<=2*(n+1-i)-1;j++)
{
printf("<H> ");
}
printf("\n");

for(j=1;j<i;j++)
{
printf(" ");
}
for(j=1;j<=2*(n+1-i)-1;j++)
{
printf("I I ");
}
printf("\n");
}
return 0;
}