C++ Arrays and Vectors

Separate variables such as score1, score2, and score3 duplicate every operation and fail when another score arrives. A container stores related values under one name and exposes a common traversal interface.

The container choice describes constraints. A fixed count and a runtime-growing sequence are different requirements. Use the standard container that owns those rules rather than manually managing a memory block.

std::array<int, 3> stores exactly three integers. It can be copied as a value, reports its size, and supports range-based loops. Unlike a built-in array, it behaves consistently with the standard container model.

The size is known in the type, so arrays with different counts have different types. Use it when that fixed count is a real invariant rather than an estimate that may change.

#include <array>
#include <iostream>

int main()
{
  std::array<int, 4> quarters{18, 24, 21, 30};
  int total{};
  for (int amount : quarters) total += amount;
  std::cout << "Annual total: " << total << '\n';
}

std::vector<int> values; begins empty. push_back appends an element, size reports the current element count, and empty states whether an element can be read. Removing or inserting elements changes positions after the operation.

Capacity is allocated storage available before another reallocation. It is an implementation concern that matters for performance and iterator validity, not a count of usable elements. Start with correctness; reserve only when a realistic expected count is known.

operator[] assumes the index is valid. at checks and throws on an invalid position. Use range-based loops when no index is required and validate externally supplied positions before access.

References and iterators into a vector can become invalid after operations that reallocate or erase elements. Do not keep one across a push_back unless the validity guarantee is understood. Reacquire it after mutation when practical.