任务一

include <stdio.h>

include<stdlib.h>

include<time.h>

define N 5

int main()
{
int number;
int i;
srand(time(0));

 for(i=0;i<N;++i){ 	

 number=rand()%65+1; 	

  printf("20238331%04d\n",number); } 

return 0;
}
问题一：在一到六十五之间随机输出整数
问题二：生成五个以20238331开头的十二位数随机学号，随机数前两位为零
任务二

include <stdio.h>

int main()
{
char c;
while((c=getchar())!=EOF){

if(c=='r')
  printf("stop!\n");
else if(c=='g')
  printf("go go go\n");
else if(c=='y')
  printf("wait a minute\n");
else
  printf("something must be wrong\n");
getchar();

}
return 0;
}

任务三

include <stdio.h>

include <stdlib.h>

include <time.h>

int main()
{
int day,chance=3;
srand(time(0));
int luckday=rand()%31+1;
printf("猜猜哪一天是你的luckday\n") ;
do{
scanf("%d",&day);
if(day==luckday)
{
printf("恭喜你，猜对了\n");
break;
}
else if(day<luckday)
{printf("你猜的日期早了\n");}
else
{ printf("你猜的日期晚了\n");}
chance--;
}
while (chance>0);
if(chance<=0){
printf("你已经没有机会了,偷偷告诉你五月的幸运日是%02d号",luckday);
}
system("pause");
return 0;
}
任务四

include <stdio.h>

include <stdlib.h>

int main()
{
int a,n,y,z;
double s;
while(scanf("%d%d",&n,&a)!=EOF){
y=a;
s=0.0;
for(z=1;z<=n;z++){
s=s+(double)z/a;
a=a+a*10;
}
printf("n= %d,a= %d,s=%f\n",n,y,s);
}
system("pause");
return 0;
}

任务五

include<stdio.h>

include<math.h>

int main(){
for(int i=1;i<=9;i++){
for(int j=1;j<=i;j++){
printf("%dx%d=%d\t",j,i,j*i);
}
printf("\n");
}
return 0;
}

任务六

include <stdio.h>

include <stdlib.h>

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

for(i=0;i<n;++i){
    for (y=1;y<=i;++y)
       printf("\t");
    for(z=2*(n-i)-1;z>0;--z)
       printf("  O\t");
       printf("\n");
    for(y=1;y<=i;++y)
       printf("\t");
    for(z=2*(n-i)-1;z>0;--z)
       printf(" <H>\t");
       printf("\n");
    for(y=1;y<=i;++y)
       printf("\t");
    for(z=2*(n-i)-1;z>0;--z)
       printf(" I I\t");
       printf("\n");}
 system("pause");
return 0;
}