实验2

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);
    }
    system("pause");
    return 0;
}

 

问题1：生成1-100的随机数

问题2：讲number固定为至少4位，不够4位前面用0来补齐

问题3：生成并打印5个学员编号

task2

#include <stdio.h>
#include <stdlib.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;
        }

        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");
    system("pause");
    return 0;
}

 

问题1：每次购买完成后将total_price重置为0，去掉程序会在多次购买时累加总价，导致计算错误

问题2：break会完全终止循环；continue只是跳过了当前的循环，但会继续执行下一次循环

问题3：没有必要，因为lin17-18已经对用户输入饮料编号的有效性进行了检查

task3

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

int main()
{
    char m;

    while(1)
    {
        scanf("%c", &m);
        getchar();
        if(m == 'r')
            printf("stop!\n");
        else if(m == 'g')
            printf("go go go\n");
        else if(m == 'y')
            printf("wait a minute\n");
        else
            printf("something must be wrong\n");
    }
    system("pause");
    return 0;
}

 

task4

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

int main()
{
    double k, sum, max, min;
    sum = 0;
    max = 0;
    min = 20000;
    printf("输入今日开销，直到输入-1终止：\n");
    do
    {
        scanf("%lf",&k);
        if(k != -1)
        {
            sum = sum + k;
            if(k > max)
                max = k;
            if(k < min)
                min = k;
        }
    }while(k != -1);
        printf("今日累计消费总额%.1f \n今日最高一笔开销%.1f \n今日最低一笔开销%.1f \n",sum, max, min);
        system("pause");
        return 0;
}

task5 

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

int main()
{
    int n;
    int i;
    int k;
    i = 0;
    srand((unsigned)time(NULL));
    n = rand() % 30 + 1;
    printf("猜猜2025年4月哪一天是你的lucky day\n开始喽，你有三次机会，猜吧（1-30）：");
    while(i < 3)
    {
        scanf("%d", &k);
        if(k > n)
            printf("你猜的日期晚了，你的lucky day在前面哦\n");
        else if(k < n)
            printf("你猜的日期早了，你的lucky day还没到呢\n");
        else if(k == n)
        {
            printf("哇，猜中了:-)\n");
            break;
        }
        i = i + 1;
        if(i < 3)
            printf("再猜：");
    }
    if(k != n)
        printf("次数用完啦。偷偷告诉你，4月你的lucky day是%d号\n", n);
    system("pause");
    return 0;
}

 

 

 

task6

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

int main()
{
    int n;
    int i, k, m;
    i = 1;
    printf("input n: ");
    scanf("%d", &n);
    while(i <= n )
    {
        m = 0;
        while(m < i - 1)
        {
            printf("\t");
            m = m + 1;
        }
        k = 0;
        while(k < 2 * (n + 1 - i) - 1)
        {
            printf(" o \t");
            k = k + 1;
        }
        printf("\n");
        m = 0;
        while(m < i - 1)
        {
            printf("\t");
            m = m + 1;
        }
        k = 0;
        while(k < 2 * (n + 1 - i) - 1)
        {
            printf("<H>\t");
            k = k + 1;
        }
        printf("\n");
        m = 0;
        while(m < i - 1)
        {
            printf("\t");
            m = m + 1;
        }
        k = 0;
        while(k < 2 * (n + 1 - i) - 1)
        {
            printf("I I\t");
            k = k + 1;
        }
        printf("\n");
        i = i + 1;
    }
    system("pause");
    return 0;
}