练习一：
line15是在1~65的范围内随机取数
这个程序生成202383310001~202383310065之间的学号
练习二:

include <stdio.h>

int main()
{
char color;

while(scanf(" %c",&color)!=EOF){
	switch(color){
		case'r':printf("stop!\n");
		break;
		case'g':printf("go go go\n");
		break;
		case'y':printf("wait a minute\n");
		break;
		default:printf("something must be wrong...\n");
	}
}
return 0;

}

练习三：

include <stdio.h>

include <stdlib.h>

include <time.h>

int main(){
int number,x,i;
srand(time(0));
number=rand()%31+1;
printf("猜猜2024年5月哪一天会是你的lucky day\n开始喽，你有三次机会，猜吧（1~31）：");
for(i=1;i<=3;i++){
scanf("%d",&x);
if(x<number)
printf("你猜的日期早了，你的lucky day还没到呢\n");
else if(x>number)
printf("你猜的日期晚了，你的lucky day在前面哦\n");
else{
printf("哇，猜中了");
return 0;
}
if(i==3)
printf("次数用完啦。偷偷告诉你，5月你的lucky day是%d号",number);
if(i<3){
printf("再猜：\n");
}
}
return 0;
}

练习四：

include <stdio.h>

int main(){
int m,n,i,a;
double s;
while(1){
m=0;
s=0.0;
scanf("%d%d",&n,&a);
for(i=1;i<=n;i++){
m=m10+a;
s=s+1.0i/m;
}
printf("n=%d,a=%d,s=%lf",n,a,s);
}
return 0;
}

练习五：

include<stdio.h>

int main(){
int i,j;

for(i=1;i<=9;i++){
    for(j=1;j<=i;j++){
        printf("%d*%d=%-3d",j,i,j*i);
    }
    printf("\n");
}
return 0;

}


练习六：

include <stdio.h>

include <stdlib.h>

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

for(i=0;i<n;++i){
    for (j=1;j<=i;++j)
        printf("\t");
    for(k=2*(n-i)-1;k>0;--k)
       printf("  O\t");
    printf("\n");
    for(j=1;j<=i;++j)
       printf("\t");
    for(k=2*(n-i)-1;k>0;--k)
       printf(" <H>\t");
    printf("\n");
    for(j=1;j<=i;++j)
       printf("\t");
    for(k=2*(n-i)-1;k>0;--k)
       printf(" I I\t");
    printf("\n");}

system("pause");
return 0;

}