实验2

实验任务1

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

#define N 5
#define N1 80
#define N2 35

int main() {
    int cnt;
    int random_major,random_no;

    srand(time(NULL)); // 以当前系统时间作为随机种子
   
    cnt = 0;
    while(cnt < N) {
        random_major = rand() % 2;
        
        if(random_major) {
            random_no = rand() % N1 + 1;
            printf("20256343%04d\n", random_no);}
        else {
            random_no = rand() % N2 + 1;
            printf("20256136%04d\n", random_no);
        }
        cnt++;
    }
    return 0;
}

运行结果截图

多次重复运行发现每次产生的随机数序列都不同

问题1：strand(time(NULL));的作用是设置随机数生成的种子

问题2：这个程序的功能是生成指定数量的随机学号

实验任务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;
        }
        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;
}

运行结果截图

问题1：如果去掉这行代码，后续购买的饮料总价会和之前的总价累加

问题2：第一处输入无效饮料编号时，跳过后续输入数量、计算价格等操作，直接回到循环开头，重新让用户输入饮料编号。第二处输入购买数量为负数时，跳过后续计算价格、投入金额等操作，直接回到循环开头，重新让用户输入饮料编号。

实验任务3

#include <stdio.h>
int main() {
    char ch;
    while (scanf("%c", &ch) != EOF) {
        if (ch == 'r') {
            printf("stop!\n");
        } else if (ch == 'g') {
            printf("go go go\n");
        } else if (ch == 'y') {
            printf("wait a minute\n");
        } else {
            printf("something must be wrong..\n");
        }
        getchar();
    }
    return 0;
}

运行结果截图

实验任务4

#include <stdio.h>
int main() {
    float expense, total = 0, max = 0, min = 20000.0;
    printf("输入今日开销，直到输入-1终止：\n");
    while (1) {
        scanf("%f", &expense);
        if (expense == -1) 
            break;
        total += expense;
        if (expense > max) 
            max = expense;
        if (expense < min) 
            min = expense;
    }
    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;
}

运行结果截图

实验任务5

#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) {
            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 || a == c || b == c) {
                if ((a*a + b*b == c*c) || (a*a + c*c == b*b) || (b*b + c*c == a*a)) {
                    printf("等腰直角三角形\n");
                } else {
                    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;
}

运行结果截图

实验任务6

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
int main() {
    int lucky_day, guess, count = 0;
    srand(time(NULL));
    lucky_day = rand() % 30 + 1; 
    printf("猜猜2025年11月哪一天是你的lucky day\n");
    while (count < 3) {
        printf("开始喽，你有三次机会，猜吧(1~30): ");
        scanf("%d", &guess);
        count++;
        if (guess == lucky_day) {
            printf("哇，猜中了:)\n");
            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");
        }
        if (count < 3) {
            printf("再猜(1~30): ");
            scanf("%d", &guess);
            count++;
            if (guess == lucky_day) {
                printf("哇，猜中了:)\n");
                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");
            }
        }
    }
    if (count == 3 && guess != lucky_day) {
        printf("次数用光啦。偷偷告诉你，11月你的lucky day是%d号\n", lucky_day);
    }
    return 0;
}

运行结果截图