实验2

实验任务1
问题1：随机生成某专业学员编号，范围在202400420001~202400420100之间
问题2：返回一个1-100之间的伪随机数
问题3：固定占4个字符宽度，不够四位在左边补0
问题4：使每一次生成的随机数不一样，删去后生成的随机数每次都一样
源代码

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#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;
}

实验任务2
源代码

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#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 (quantity == 0) {
			printf("购买数量不能为0，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);

		
		if (amount_paid < total_price) {
			printf("金额不足，无法完成购买！\n");
			total_price = 0;
			continue;
		}

		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：如果去掉，没有重新重置total_price为0，在第二次运算时total_price为第一次计算的值，导致数据错误
问题2∶在循环中使用 continue 语句，语义是满足该条件语句后则跳过本次循环
实验任务3

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#include <stdio.h>
int main() {
    char ch;
    while (scanf(" %c", &ch) != EOF) {
        switch (ch) {
            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;
}

实验任务4

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#include <stdio.h>

int main() {
    double sum = 0.0;    
    double max = 0.0;    
    double min = 20001.0;
    double money;        
    printf("输入今日开销，直到输入-1终止:\n");

    while (1) {
        scanf("%lf", &money);
        if (money == -1) {
            break; 
        }
        sum += money;
        if (money > max) {
            max = money;
        }
        if (money < min) {
            min = money;
        }
    }
    printf("今日累计消费总额: %.1f\n", sum);
    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;
}

实验任务5

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#include <stdio.h>

int main() {
    int a, b, c;
    while (scanf("%d %d %d", &a, &b, &c) == 3) {
        int x = a, y = b, z = c;
        int temp;
        if (x > y) 
		{ temp = x;
		  x = y; 
		  y = temp; 
		}
        if (x > z) 
		{ temp = x;
		  x = z; 
		  z = temp;
		}
        if (y > z)
		{ temp = y;
		   y = z; 
		   z = temp;
		}
        if (x + y <= z) {
            printf("不能构成三角形\n");
            continue; 
        }
        if (x == y && y == z) {
            printf("等边三角形\n");
        } else if (x == y || y == z || x == z) {
            printf("等腰三角形\n");
        } else if ((long long)x * x + (long long)y * y == (long long)z * z) 
		{
            printf("直角三角形\n");
        } else {
            printf("普通三角形\n");
        }
    }

    return 0;
}

实验任务6

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#include <stdio.h>
#include <stdlib.h>
#include <time.h>
int main() {
    int lucky, guess, i;
    srand((unsigned int)time(NULL));
    lucky = rand() % 30 + 1;

    printf("猜猜2026年4月哪一天是你的lucky day\n");
    printf("开始喽，你有3次机会，猜吧(1~30)：");
    for (i = 0; i < 3; i++) {
        scanf("%d", &guess);
		}
        if (guess == lucky) {
            printf("哇，猜中了:)\n");
            return 0; 
        }
	    else if (guess > lucky) {
            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 (i < 2) {
            printf("再猜(1~30)：");
        }
    }
    printf("次数用光啦。4月你的lucky day是%d号\n", lucky);

    return 0;
}