实验二

task1

#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() % 100 + 1;
		printf("20490042%04d\n",number);
	}
	
	return 0;
}

　　 问题1：随机抽取5个编号

        问题2：以当前时间为变量取最后四个数字

        问题3：最后四个数字赋值

        问题4：不管编译几次 抽到的编号都一样

task2

#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;
}

　　问题1：会把上一次输入的price累积加入到下一次的输入

       问题2：结束这一次运行，重新开始这一循环

task3

#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");break;
    	}	
	}
  
	return 0;
}

　　

task4

#include<stdio.h>

int main(){
	float price, total = 0, max = 0, min = 2001;
	int count = 0;
	
	printf("输入今日开销，直到输入-1终止：\n");
	
	while(1){
		scanf("%f",&price);
		if(price == -1){
			break;
		}
		if(price<=0||price>20000){
			continue;
		}
		total += price;
		if(price>max){
			max = price;
		}
		if(price <min){
			min = price;
		}
		count++;
	} 
    printf("今日累计消费总额：%.1f\n", total);
    printf("今日最高一笔开销：%.1f\n", max);
    printf("今日最低一笔开销：%.1f\n", min);
   
    return 0; 
}
 

　　

task5

#include <stdio.h>

int main() {
    int a, b, c;
    while (scanf("%d %d %d", &a, &b, &c) != EOF) {
        if (a + b <= c || a + c <= b || b + c <= a || a <= 0 || b <= 0 || c <= 0) {
            printf("不能构成三角形\n");
        } else {
            if (a == b && b == c) {
                printf("等边三角形\n");
            } else if (a == b || b == c || a == c) {
                printf("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("直角三角形\n");
            } else {
                printf("普通三角形\n");
            }
        }
    }
    return 0;
}

　　

问题6

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

int main() {
    int lucky_day, guess, chances = 3;

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

    printf("\n猜猜2026年4月哪一天是你的lucky day\n");
    printf("开始喽，你有%d次机会，猜吧(1~30)：", chances);
    scanf("%d", &guess);

    while (chances > 1) {
        if (guess == lucky_day) {
                break;
            }
	    else if (guess > lucky_day) {
                printf("你猜的日期晚了，你的lucky day在前面哦\n");
            } 
		else {
                printf("你猜的日期早了，你的lucky day还没到呢\n");
            }

            chances--;
            printf("再猜(1~30)：");
            scanf("%d", &guess);
        }

        if (guess == lucky_day) {
            printf("哇，猜中了！\n");
        }
		 else {
            printf("次数用完啦。4月你的lucky day是%d号\n", lucky_day);
        }

    return 0;
}