A bank account class – OOP in C++ Practice Problem

Complete the class Account, whose balance is private and starts at 0. Handle these commands:

deposit x: add x to the balance, if x > 0; otherwise print error.
withdraw x: take x from the balance, if 0 < x ≤ balance; otherwise print error.
balance: print the balance.

What to build

A bank account class whose balance can change only through checked member functions.

Requirements

Keep the balance private, starting at 0.
Make deposit and withdraw return false when the amount is not allowed.
Print error whenever a command fails.

Input

The first line has q (1 ≤ q ≤ 1000). Each of the next q lines has one command; amounts are whole numbers.

Output

One line for each balance command and for each command that fails.

Constraints

1 ≤ q ≤ 1000, and the amounts are whole numbers.

Example

Input:

4
deposit 500
withdraw 800
withdraw 200
balance

Output:

error
300

Why it works

Because the balance is private, every change goes through deposit or withdraw, which check the amount first. No other code can put the account into a wrong state.

Examples

Example 1 · Input

4
deposit 500
withdraw 800
withdraw 200
balance

Expected output

error
300

Example 2 · Input

3
deposit -5
balance
withdraw 0

Expected output

error
0
error

Hints

Hint 1

Keep balance private; deposit and withdraw return false when the amount is not allowed.

Hint 2

A deposit must be positive; a withdrawal must be positive and not more than the balance.

Hint 3

Print error when deposit or withdraw returns false.

Solution

Show one correct solution (try it yourself first)

#include <iostream>
#include <string>
using namespace std;

class Account {
    long long balance;
public:
    Account() : balance(0) {}
    bool deposit(long long x) {
        if (x <= 0) return false;
        balance += x;
        return true;
    }
    bool withdraw(long long x) {
        if (x <= 0 || x > balance) return false;
        balance -= x;
        return true;
    }
    long long getBalance() const {
        return balance;
    }
};

int main() {
    Account acc;
    int q;
    cin >> q;
    for (int i = 0; i < q; i++) {
        string cmd;
        cin >> cmd;
        if (cmd == "balance") {
            cout << acc.getBalance() << endl;
            continue;
        }
        long long x;
        cin >> x;
        bool ok = cmd == "deposit" ? acc.deposit(x) : acc.withdraw(x);
        if (!ok) cout << "error" << endl;
    }
    return 0;
}

Lesson: Classes and objects →