Comic 001 – Reverse Integer

When your int can’t handle Gangnam Style 💃

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🧩 Problem

On LeetCode, “Reverse Integer” looks simple:
👉 Take an integer, flip its digits, return the result.

But here’s the catch: what if the reversed number overflows a 32-bit integer?
💥 Suddenly, your program crashes.

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💻 Code Example (C++)

#include <iostream>
#include <climits> // for INT_MAX and INT_MIN
using namespace std;

class Solution {
public:
    int reverse(int x) {
        int rev = 0;
        while (x != 0) {
            int digit = x % 10;
            x /= 10;

            // Check for overflow before multiplying by 10
            if (rev > INT_MAX / 10 || (rev == INT_MAX / 10 && digit > 7)) {
                return 0; // overflow
            }
            if (rev < INT_MIN / 10 || (rev == INT_MIN / 10 && digit < -8)) {
                return 0; // underflow
            }

            rev = rev * 10 + digit;
        }
        return rev;
    }
};

int main() {
    Solution s;
    cout << s.reverse(123) << endl;   // Output: 321
    cout << s.reverse(-123) << endl;  // Output: -321
    cout << s.reverse(120) << endl;   // Output: 21
    cout << s.reverse(1534236469) << endl; // Output: 0 (overflow)
    return 0;
}

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🌍 Real-World Connection

Think of YouTube’s view counter.
Every time a video racks up millions of views, the counter increments.

But if the system isn’t overflow-safe…
➡️ 2 billion views could turn into negative views or break the counter.

This tiny puzzle reflects a massive engineering challenge:

• Handling edge cases at scale
• Designing systems that fail gracefully
• Thinking like an engineer, not just a coder

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🛠 How It’s Solved in the Real World

Our code above works for LeetCode: if overflow happens, we just return 0.
But production systems don’t have that luxury.

• Bigger data types
  YouTube originally used a 32-bit signed integer for view counts (max 2,147,483,647).
  In 2014, Psy’s Gangnam Style broke this limit.
  Solution? Upgrade to a 64-bit counter (max 9,223,372,036,854,775,807). Problem solved (for now 😉).

• Even bigger numbers
  In cryptography, finance, and scientific computing, numbers can exceed 64-bit.
  Engineers use tools like GMP (GNU Multiple Precision) or even __int128 in GCC/Clang.

• Scaling / Approximation
  Social platforms don’t show exact numbers past a point.
  • Backend stores the raw number safely (long long or bigger).
  • Frontend shows a friendly version: 1.2B instead of 1,234,567,890.
  • Keeps the UI neat while data stays safe.
• Graceful handling
  Instead of silently failing, production systems may:
  • Log the overflow
  • Throw an exception
  • Use fallback values

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⚡ Takeaway

DSA isn’t just about algorithms. It’s about building systems that stand strong in the real world.

👉 Next time you solve a DSA problem, ask: “Where does this live in the real world?”

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📅 Published: September 2025 ✍️ Author: Aisha Karigar