为何计算出的总金额为0？C++存钱罐代码问题排查

我运行一段C++存钱罐程序时，总金额始终显示为0。该程序应接收paper、coins、cents三类金额输入并计算总金额，代码如下：

int coins = 0;
int paper = 0;
int cents = 0;
int transaction = 0;
int total_money = coins + paper + cents;

cout << "Do you want to fill your piggy bank?";
cin >> transaction;

while (transaction != 2)
{
    cout << "How many paper money? :";
    cin >> paper;
    cout << "How many coins ? :";
    cin >> coins;
    cout << "How many cents? :";
    cin >> cents;
    cout << "Do you want another transaction?";
    cin >> transaction;
    if (transaction == 2)
    {
        cout << "total in piggy bank" << total_money << endl;
    }
    else
    {
        cout << "End of the program";
    }

    return 0;
}

问题点分析 #

• 总金额计算时机错误：total_money在变量初始化时就被赋值为0（因为此时coins、paper、cents都是初始的0），后续用户输入新的金额值后，程序不会自动重新计算total_money，所以它的值永远是0。必须在每次用户输入完金额后，重新执行total_money = coins + paper + cents;（如果是累加多次交易，就用total_money += paper + coins + cents;）来更新总金额。
• 循环提前终止：return 0;写在了while循环的内部，第一次循环执行到这里就会直接退出整个程序，循环根本无法重复执行，用户连一次完整的交易流程都走不完。
• 分支逻辑混乱：当用户输入的transaction不等于2时，直接输出"End of the program"，但此时用户可能想继续交易（比如输入1），这部分逻辑完全不符合需求。正确逻辑应该是：只有当transaction等于2时，计算并显示总金额；否则回到循环开头，进行下一次交易。

修正后的示例代码 #

#include <iostream>
using namespace std;

int main()
{
    int coins = 0;
    int paper = 0;
    int cents = 0;
    int transaction = 0;
    int total_money = 0;

    cout << "Do you want to fill your piggy bank? (1=Yes, 2=No): ";
    cin >> transaction;

    while (transaction != 2)
    {
        cout << "How many paper money? : ";
        cin >> paper;
        cout << "How many coins ? : ";
        cin >> coins;
        cout << "How many cents? : ";
        cin >> cents;
        // 每次输入后累加计算总金额
        total_money += paper + coins + cents;

        cout << "Do you want another transaction? (1=Yes, 2=No): ";
        cin >> transaction;
    }
    // 退出循环后统一显示总金额
    cout << "Total in piggy bank: " << total_money << endl;
    return 0;
}

内容的提问来源于stack exchange，提问作者Dexter Hecali