C++自动售货机开发：如何用for循环计算用户输入的累计金额？

首先你的代码存在几个关键问题需要修正：

1. while循环条件逻辑错误：while (choice == 1 || 2 || 3) 的写法不符合语法规范，正确的逻辑判断应该是 while (choice == 1 || choice == 2 || choice == 3)，否则数字2、3会被当作布尔值true，导致循环永远无法终止。

2. for循环完全误用：你嵌套的for循环语法错误（i = true是赋值操作而非判断），且这种场景根本不需要嵌套循环。作业要求使用for循环，其实可以用它来遍历所有饮料的购买数量与单价，累加计算总价，这才是符合要求的用法。

以下是修正后的完整代码，重点实现了for循环计算总价的逻辑：

#include <iostream>
using namespace std;

int main() {
    int choice = 0;
    int amount1 = 0, amount2 = 0, amount3 = 0;
    // 用数组存储饮料单价和对应购买数量，方便for循环遍历
    float drinkPrices[] = {1.0, 0.5, 0.25};
    int drinkAmounts[] = {amount1, amount2, amount3};
    int drinkCount = sizeof(drinkPrices) / sizeof(drinkPrices[0]);

    // 改为当用户未选择"结算"时持续循环
    while (choice != 4) {
        cout << "Available sodas and prices:" << endl;
        cout << "1. Coke - $1" << endl;
        cout << "2. Pepsi - $0.50" << endl;
        cout << "3. Root Beer - $0.25" << endl;
        cout << "4. Finish and calculate total" << endl;
        cout << "Please enter the number of the soda you would like to purchase: ";
        cin >> choice;

        if (choice == 1)
        {
            cout << "How many Cokes would you like?: ";
            cin >> amount1;
            cout << "The total amount for " << amount1 << " Cokes is: $" << amount1 * 1 << endl;
        }
        else if (choice == 2)
        {
            cout << "How many Pepsi would you like?: ";
            cin >> amount2;
            cout << "The total amount for " << amount2 << " Pepsi is: $" << amount2 * 0.5 << endl;
        }
        else if (choice == 3)
        {
            cout << "How many Root Beers would you like?: ";
            cin >> amount3;
            cout << "The total amount for " << amount3 << " Root Beers is: $" << amount3 * 0.25 << endl;
        }
        else if (choice == 4)
        {
            // 更新数组中的最新购买数量
            drinkAmounts[0] = amount1;
            drinkAmounts[1] = amount2;
            drinkAmounts[2] = amount3;

            float total = 0.0;
            // 用for循环遍历所有饮料，累加计算总价
            for (int i = 0; i < drinkCount; i++) {
                total += drinkAmounts[i] * drinkPrices[i];
            }

            cout << "Your total cost today is: $" << total << ". Thank you for shopping at the Soda Shop!" << endl;
            return 0;
        }
        else {
            cout << "Invalid option. Please select a valid soda choice or choose 4 to finish." << endl;
        }
        cout << endl;
    }
    return 0;
}

关于for循环的说明 #

这里用for循环的核心目的是批量处理所有饮料的总价计算：遍历每种饮料的购买数量和对应单价，将单种饮料的总价（数量×单价）累加到总金额中。这种写法不仅满足作业要求，还具备扩展性——如果后续新增饮料，只需在数组中添加对应的价格和数量变量，无需修改计算逻辑。

内容的提问来源于stack exchange，提问作者NazrimLoop