代码有效 数学不行

Question

我的代码编译得很好，但我使用的数学公式没有提供正确的结果。我需要计算所有 3 个月的余额、提取和利息。我还需要验证用户的输入。出于这些目的，我使用嵌套循环。如果您发现我的错误，请告诉我。谢谢可爱的人！

cout << "Please enter the starting balance: ";
cin  >>  startBalance;  
cout << "Please enter the annual interest rate: ";
cin  >> annualInterest;
for (int month = 1; month <= 3; month++) {
       do { 
        cout << setprecision(5);
        cout << "Please enter the total amount deposited on month " << month << ": ";
        cin >> balance; 
        if (balance <0)  {  
            goodChoice = false;
            cout << "nt***ERROR " << balance << " ***";
            cout << "*** Choice must be positive***n" << endl;
            }
            else {
             goodChoice = true;
            }
        startBalance += balance; //need to calculate the balance for all 3 months
           } while (!goodChoice); 
       do { 
        cout << setprecision(5);
        cout << "Please enter the total amount withdrawn on " << month << ": ";
        cin >> withdrawn; 
            if ( (withdrawn <0) || (withdrawn > startBalance) ) {  
            goodChoice = false;
            cout << "***ERROR " << withdrawn << " ***";
            cout << "*** Choice must be positive or greater than the balance***" << endl;
            }
            else {
             goodChoice = true;
            }
             finalWithdrawn += withdrawn; // the total amount of withdrawn
             finalBalance = startBalance - withdrawn;
          monthInterest = ((startBalance + finalBalance) / 2) * (annualInterest / 12);
          totalInterest += monthInterest; //total interest for all 3 months
          endBalance = monthInterest + finalBalance;

        } while (!goodChoice);  
}
cout << "Total Deposit: " << endBalance << endl;
cout << "Total Withdrawn: " << finalWithdrawn << endl;
cout << "Total Interest: " << totalInterest << endl;
cout << "Final Balance: " << endBalance << endl;

Answer 1

你定义了很多不需要的额外变量。此外，您的利率可能是百分比而不是十进制数字，即 10% = 0.1。此外，您的monthInterest取平均值，然后应用利息。我写了这个，它似乎有效。

#include <iostream>
#include <iomanip>
using namespace std;
int main()
{
    float totalDeposit = 0.0f;
    float totalWithdrawn = 0.0f;
    float totalInterest = 0.0f;
    float totalBalance = 0.0f;
    float interestRate = 0.0f;
    setprecision(5); //?
    cout << "Enter starting balance: ";
    cin >> totalBalance;
    cout << "Enter annual interest rate (%): ";
    cin >> interestRate;
    // Convert to monthly and non-percent; i.e. 10% = 0.1 = 10 / 100
    interestRate = interestRate / 100.0f / 12.0f;
    for (int month = 1; month <= 3; month++)
    {
        float deposit = -1.0; // Default to an error state
        while (deposit < 0.0)
        {
            cout << "Enter total deposited in month " << month << ": ";
            cin >> deposit;
            if (deposit < 0.0f)
            {
                cout << "ERROR: Invalid amount" << endl;
                continue;
            }
        }
        float withdrawn = -1.0f; // Default to an error state
        while (withdrawn < 0.0f)
        {
            cout << "Enter total withdrawn in month " << month << ": ";
            cin >> withdrawn;
            if (withdrawn < 0.0f)
            {
                cout << "ERROR: Invalid amount" << endl;
                continue;
            }
        }
        totalDeposit += deposit;
        totalWithdrawn += withdrawn;
        totalBalance = totalBalance + deposit - withdrawn;
        totalBalance += totalBalance * interestRate;
        totalInterest += totalBalance * interestRate;
    }
    cout << "Total Deposit: " << totalDeposit << endl;
    cout << "Total Withdrawn: " << totalWithdrawn << endl;
    cout << "Total Interest: " << totalInterest << endl;
    cout << "Final Balance: " << totalBalance << endl;
    int wait; // Pause so console window doesn't close. Delete this line.
    cin >> wait;
    return 0;
}