实验2

实验任务1：

#include<stdio.h>
#include<stdlib.h>
#include<time.h>
int main(){
#define N 5
#define N1 80
#define N2 35
int cut;
int random_major,random_no;

cut = 0;
while(cut<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);

}
cut++;
}
return 0;
} 

问题1：当删掉代码时，可以发现生成的学号是固定的，说明代码的作用就是为了生成随机数字

问题2：此程序的作用是生成学号。

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;
break;
}

printf("感谢您的购买，欢迎下次光临！\n");
return 0;
}

问题1：去掉total-price=0，可以看见第二次购买时，购买总价出现了与上一次叠加，使得结果出现问题。

问题2：用continue跳出本次循环，直接进行下一次循环。

实验任务3：

#include<stdio.h>
int main(){
char ans;
scanf(" %c",&ans);

while(scanf(" %c", &ans) != EOF){ //ctrl+z
if(ans == 'r')
{
printf("stop!\n");
}
else if(ans == 'g')
{
printf("go go go\n");
}
else if(ans == 'y')
{
printf("wait a minute\n");
}
else
{
printf("something must be wrong\n");
}
}

return 0;
}

实验任务4：

#include <stdio.h>
int main() {
float expense, total = 0, max = 0, min = 20000;

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;
}

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");
continue;
}

if(a == b && b == c){
printf("等边三角形\n");
}
else if(a == b || b == c || a == c){//等边优先级大于等腰
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;
}

实验任务6;

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

int main() {
srand(time(NULL));

int lucky_day = rand() % 30 + 1;
int guess;
int attempts = 0;
int guessed = 0;

printf("猜猜2025年11月哪天是你的lucky day\n");
printf("开始哦，你有三次机会，猜吧(1~30)：");

while (attempts < 3) {
scanf("%d", &guess);
attempts++;

if (guess == lucky_day) {
printf("哇，猜中了 :)\n");
guessed = 1;
break;
} else if (guess < lucky_day) {
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 < 3) {
printf("再猜(1~30)：");
}
}

if (!guessed) {
printf("次数用光啦。偷偷告诉你，11月份的lucky day是%d号\n", lucky_day);
}

return 0;
}