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)); // 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;
}

line13代码功能：随机生成1~100数字赋值给number

%04d作用：使number数字补足4位，不足四位前面加0

代码作用：随机生成一位学员学号202400420001~202400420100.

Task 2

#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;
        }
        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;
}

 

line53作用：将价格重新归零，如果删去会使价格初始值与上一次支付相同

break是跳出内循环，continue是继续内循环

不用加入default语句，因为choice一定在规定范围之内

 

Task3

#include <stdio.h>
int main()
{
    char s;
    while (1) {
        scanf_s("%c", &s,1);
        getchar();
        switch (s) {
        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;

如果输入一串字符，会导致产生BUG

Task4

 

#include <stdio.h>
int main()
{
    double sum = 0, a, b = 0, c = 20000;
    printf("输入今日开销，直到输入-1终止：");
    while (1) {
        scanf("%lf", &a);
        if (a == -1) {
            break;
        }
        sum = sum + a;
        if (c > a) {
            c = a;
        }
        if (b < a) {
            b = a;
        }
    }
    printf("今日累计消费总额：%.1f\n", sum);
    printf("今日最高一笔开销：%.1f\n", b);
    printf("今日最低一笔开销：%.1f\n", c);

    return 0;
}

Task5

#include <stdio.h>
#include <stdlib.h>
int main()
{
    int day, s, i;
    printf("猜猜2025年4月哪一天是你的lucky day");
    day = rand() % 30 + 1;
    printf("开始喽，你有三次机会，猜吧（1~30）：");
    scanf("%d", &s);
    for (i = 0; i < 2; ++i) {
        if (s < day) {
            printf("你猜的日期早了，你的lucky day还没到呢\n");
        }
        if (s > day) {
            printf("你猜的日期晚了，你的lucky day总会到的\n");
        }
        printf("再猜（1~30）");
        if (s == day) {
            printf("哇，猜中了：-）");
            break;
        }
        scanf("%d", &s);
    }
    if (s != day) {
        printf("次数用完了。偷偷告诉你，4月你的lucky day是%d号", day);
    }
    return 0;

}

Task6

#include <stdio.h>

int main() {
    int n;
    printf("input n: ");
    scanf_s("%d", &n);

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

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

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

    return 0;
}