实验2

实验任务1

#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：生成1~100的随机整数

问题2：格式化输出整数number使其至少有四位数字，若不足四位前面会用0填充。

问题3：生成五个随机学号，且五个学号前缀一样，即前8位数字相同。

实验任务2

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;
        }

        switch (choice) {
            case 1:
            case 2:
                total_price += 3 * quantity;
                break;
            case 3:
                total_price += 5 * quantity;
                break;
            case 4:
                total_price += 2 * quantity;
                break;
        }

        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：重置变量为0，便于计算下次购买金额；若缺少会将本次的购买金额加入到下次的购买金额中。

问题2：break会直接跳出整个循环并不再执行循环中的任何代码；continue会跳出本次循环的剩余部分，但会继续执行下个循环。

问题3：有必要；原因：在当前代码中，若输入一个不在1~4范围内的数字，程序会打印一条错误信息并重新执行下一次循环，但若没有default子句，程序不会明确指出该情况被处理过。

实验任务3

 

#include<stdio.h> 
int main()
{
    char light;
while(1){    
printf("请输入交通信号灯颜色：");
    light=getchar();
    getchar();
switch(light){
case'r':printf("stop\n");
    break;
case'g':printf("gogogo\n");
    break;
case'y':printf("wait a moment\n");
    break;
default:
    printf("something must be wrong...\n");
    break;
}
  }
    return 0;
    }
    

 实验任务4

#include <stdio.h>

int main() {
    double expense, maxExpense = 0, minExpense = 20000, totalExpense = 0;
    int isFirst = 1;

    printf("输入今日开销，直到输入 -1 终止：\n");

    while (1) {
        scanf("%lf", &expense);
        if (expense == -1) {
            break;
        }
        if (expense <= 0 || expense > 20000) {
            printf("输入的开销必须大于0且不超过20000元。\n");
            continue;
        }

        if (isFirst) {
            maxExpense = minExpense = expense;
            isFirst = 0;
        } else {
            if (expense > maxExpense) {
                maxExpense = expense;
            }
            if (expense < minExpense) {
                minExpense = expense;
            }
        }
        totalExpense += expense;
    }

    printf("今日累计消费总额：%.1f\n", totalExpense);
    printf("今日最高一笔开销：%.1f\n", maxExpense);
    printf("今日最低一笔开销：%.1f\n", minExpense);

    return 0;
}

 实验任务5

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

int main() {
    int luckyDay, guess, attempts = 0;
    const int maxAttempts = 3;
    srand((unsigned int)time(NULL));
    luckyDay = rand() % 30 + 1;
    printf("猜猜2025年4月哪一天是你的lucky day\n");
    printf("开始喽，你有三次机会，猜吧(1~30)：");

    for (attempts = 0; attempts < maxAttempts; attempts++) {
        scanf("%d", &guess);
        if (guess == luckyDay) {
            printf("哇，猜中了:-)\n");
            return 0;
        } else if (guess < luckyDay) {
            printf("你猜的日期早了，你的lucky day还没到呢\n");
        } else {
            printf("你猜的日期晚了，你的lucky day在前面哦\n");
        }
        if (attempts < maxAttempts - 1) {
            printf("再猜(1~30)：");
        }
    }

    printf("次数用完啦。偷偷告诉你，4月你的lucky day是%d号\n", luckyDay);

    return 0;
}

 实验任务6

 

#include <stdio.h>
#include <stdlib.h>
int main()
{
int n,i,j;

scanf("%d",&n);
for (i=n;i>=1;--i)
{
for (j=0;j<n-i;++j)
{
printf(" ");
}
for (j = 0; j < 2 * i - 1; ++j)
{
printf(" 0 ");
printf(" ");
}
printf("\n");
for (j=0;j<n-i;++j)
{
printf(" ");
}
for (j=0;j<2*i-1;++j)
{
printf("<H>");
printf(" ");
}
printf("\n");
for (j=0;j<n-i;++j)
{
printf(" ");
}
for (j = 0; j < 2 * i - 1; ++j)
{
printf("I I");
printf(" ");

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