When to use std::vector vs std::array

The choice between std::vector and std::array depends on your specific requirements:

Use std::vector when:

• You need a resizable array whose size can change at runtime
• You don't know the number of elements at compile time
• You want to efficiently add or remove elements from the end of the array

1#include <iostream>
2#include <vector>
3
4int main() {
5  std::vector<int> vec{1, 2, 3};
6  vec.push_back(4);  
7  std::cout << "Vector size: " << vec.size();
8}

1Vector size: 4

Use std::array when:

• You know the number of elements at compile time
• You want a fixed-size array that cannot change size at runtime
• You want to avoid dynamic memory allocation overhead

1#include <array>
2#include <iostream>
3
4int main() {
5  std::array<int, 3> arr{1, 2, 3};
6  // arr.push_back(4); // Compile error 
7  std::cout << "Array size: " << arr.size();
8}

1Array size: 3

In general, prefer std::array for fixed-size arrays and std::vector for dynamic arrays.