Скачать или смотреть 👉 Two Sum II Explained for Beginners | 0-Based vs 1-Based Indexing | C++

In this video, we solve LeetCode 167 – Two Sum II using the Two Pointer technique in C++.

But many beginners get confused about one BIG question:

👉 If the problem says index is 1-based, why do we start from 0 in the code?

Let’s understand this clearly 👇

✅ Arrays in C++ always use 0-based indexing
That means the first element is stored at index 0, not 1.

✅ We start from left = 0 because that is how memory and arrays work internally.

✅ The problem only asks us to RETURN the answer in 1-based indexing.

👉 So after finding the correct pair, we simply return:

{left + 1, right + 1}
✔️ Internal work → 0-based
✔️ Final answer → Convert to 1-based

Simple and professional approach 🚀

Always remember:
Programming arrays use 0-based indexing, even if the problem asks for 1-based output.

Just convert before returning!

⏰ Complexity

👉 Time Complexity: O(n)
👉 Space Complexity: O(1)

#leetcode #twopointers #cpp #dsa #codingforbeginners #programming #softwareengineer