C++ - lesson 1 | HackIndia Skills

C++ - lesson 1 | HackIndia Skills | HackIndia

Example

Before and after

This small program reads daily expenses and prints the total. The safe version checks input, rejects negative counts, and never reads outside the vector.

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

int main() {
    int n = 0;
    if (!(cin >> n)) {
        cout << "Invalid count\n";
        return 1;
    }

    if (n < 0) {
        cout << "Count cannot be negative\n";
        return 1;
    }

    vector<int> expenses(n);
    for (int i = 0; i < n; i++) {
        if (!(cin >> expenses[i])) {
            cout << "Invalid expense\n";
            return 1;
        }
        if (expenses[i] < 0) {
            cout << "Expense cannot be negative\n";
            return 1;
        }
    }

    long long total = 0;
    for (int amount : expenses) {
        total += amount;
    }

    cout << total << "\n";
    return 0;
}

// Sample input:
// 4
// 120 50 30 200
// Output:
// 400

Your repo habit

From lesson one, keep sample input near your code. A future internship reviewer should be able to run your program without guessing what to type.

For now, a simple input.txt is enough. Later you will improve build instructions and README structure.

// input.txt
4
120 50 30 200

Write C++ that does not break

Why this matters

One rule

Write safer basics

Silent wrong code

Before and after

Use AI carefully

Your repo habit

Do this now

Quick check