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🧠 Is dynamic memory (using new and delete) necessary in C++?

βœ… Short Answer:

No, it’s not always necessary.


πŸ” When You DON'T Need Dynamic Memory:

You already know the size at compile time, like:

int arr[100]; // βœ… works fine, fixed size

Even for small programs where max size is safe (like 1000), this is fine:

int arr[1000];

πŸ”₯ Competitive programming / beginner DSA often uses this fixed-size array.


❌ When Fixed Arrays Fail:

If the user gives input at runtime, and you don't know the size:

int N;
cin >> N;
int arr[N]; // ❌ Not allowed in standard C++

βœ… Solution:

Use dynamic memory:

int* arr = new int[N]; // Allocates N-size array during runtime

🧼 Is delete[] necessary?

Yes, when you use new, you must manually free memory:

delete[] arr;

If you don’t, it causes a memory leak β€” bad in long-running programs.


πŸ’‘ Pro Tip:

In real-world C++, we use:

#include <vector>
vector<int> arr(N); // Dynamic & auto memory managed βœ…

But for now, you're learning raw arrays β€” so stick to:

  • new + delete[] if size is dynamic
  • fixed arrays if size is known or maxed out

βœ… Summary:

Situation Use What?
Known size (e.g., 100) int arr[100]; βœ…
Unknown size at runtime int* arr = new int[N]; βœ…
Advanced C++ / safer method vector<int> arr(N); βœ…

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