实验二

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#define N 5
int main() {
   int number;
   int i;
 srand(time(0)); // 以当前系统时间作为随机种子
 for(i = 0; i < N; ++i) {
 number = rand() % 100 + 1;
 printf("20490042%04d\n", number);
 }
 return 0;}

1.随机生成并打印N个符合格式的学号

2.生成1-100之间的随机整数，作为学号编号的后四位数

3.控制输出格式为十进制

4.实现随机生成数的目的；导致程序出现伪随机

#include <stdio.h>
int main() {
int choice, quantity;
float total_price = 0, amount_paid, change;
while (1) {
printf("\n自动饮料售卖机菜单:\n");
printf("1. 可乐 - 3 元/瓶\n");
printf("2. 雪碧 - 3 元/瓶\n");
printf("3. 橙汁 - 5 元/瓶\n");
printf("4. 矿泉水 - 2 元/瓶\n");
printf("0. 退出购买流程\n");
printf("请输入饮料编号: ");
scanf("%d", &choice);
if(choice==0)
break;
if (choice < 1 || choice > 4) {
printf("无效的饮料编号，请重新输入。\n");
 continue; }
 printf("请输入购买的数量: ");
 scanf("%d", &quantity);
 if (quantity < 0) {
 printf("购买数量不能为负数，请重新输入。\n");
 continue;}
 if(choice == 1 || choice == 2)
 total_price += 3 * quantity;
 else if(choice == 3)
total_price += 5 * quantity;
else
total_price += 2 * quantity;
 printf("请投入金额: ");
 scanf("%f", &amount_paid);
 change = amount_paid - total_price;
 printf("本次购买总价: %.2f 元\n", total_price);
 printf("找零: %.2f 元\n", change);
 total_price = 0;}
 printf("感谢您的购买，欢迎下次光临！\n");
 return 0;}

1.总价累加错误

2.过滤无效输入或者终止当前流程

#include<stdio.h>
int main(){
    char ans1;
    printf("请输入字符来表示信号灯的颜色\n");
    while((ans1=getchar())!=EOF){
        if(ans1=='\n'){
        continue;}
        if(ans1=='r'){
            printf("Stop!\n");
        }else if(ans1=='g'){
            printf("gogogo\n");
        }else if(ans1=='y'){
            printf("wait a mintue\n");
        }else{
            printf("wrong\n");
        }
    }
    return 0;
    
     
}

#include<stdio.h>
int main(){
    double expense,total=0,max_expense,min_expense;
    int count=0;
    printf("请输入今天的若干笔开销，直到输入-1终止\n");
    while(1){
        scanf("%lf",&expense);
    if(expense==-1){
        break;
    }
    if(expense<0||expense>20000){
      printf("输入错误\n");
      continue; }
     total+=expense;
     count++;
     if(count==1){
         max_expense=min_expense=expense;
     }else{
         if(expense>max_expense){
          max_expense=expense;
         }
        if(expense<min_expense){
            min_expense=expense;
        }
     }
}
    if(count==0){
        printf("输入有误，请重新输入\n");
    }else{
       printf("今日消费总额：%lf\n",total);
       printf("今日消费最高额为：%lf\n",max_expense);
       printf("今日消费最低额为：%lf\n",min_expense);
    }
    return 0;
     
}

#include<stdio.h>
int main(){
    int a,b,c;
    printf("输入三角形的三边长：\n");
    while(scanf("%d %d %d",&a,&b,&c)!=EOF){
    if(a<=0||b<=0||c<=0||a+b<=c||a+c<=b||b+c<=a){
        printf("不能形成三角形\n");
        continue;
        }
    if(a==b&&b==c){
        printf("三角形为等边三角形\n"); 
    }else if(a==b||a==c||b==c){
        printf("三角形为等腰三角形\n"); 
    }else if(a*a+b*b==c*c||a*a+c*c==b*b||b*b+c*c==a*a){
        printf("三角形是直角三角形\n"); 
    }else{
        printf("三角形是普通三角形\n"); 
    }
    
}
   return 0;
}

#include<stdio.h>
#include<stdlib.h>
#include<time.h>
int main(){
    int i;
    srand(time(NULL));
    printf("猜猜四月哪天是你的幸运天吧，你有三次机会（1-30）\n");
    int day=rand()%30+1;
    for(i=0;i<3;i++){
        int guess;
        scanf("%d",&guess);
         if(guess<day){
            printf("早啦\n"); 
        }
        else if(guess>day){
            printf("晚啦\n");
        }else if(guess=day){
            printf("猜对啦\n");
            return 0;}
    }
        printf("机会用完了，你的lucky day是%d\n",day);
    }