Why is the vector class in C++ implemented through data duplication during copying or insertion?

In C++, the std::vector class is implemented with data copying during copy or insert operations to ensure object independence and memory management safety. When copying, the vector creates its own buffer and copies the elements so that changes in one object do not affect the other. This prevents issues with double freeing of memory and ensures predictable behavior.

This approach aligns with the semantics of value types in C++, where a copy of an object should be fully independent. Although it may lead to additional time and memory costs, it simplifies resource management and prevents errors.

Example of copying a vector:

#include <vector>
#include <iostream>

int main() {
    std::vector<int> v1 = {1, 2, 3};
    std::vector<int> v2 = v1; // creates a copy of data
    v2[0] = 10;
    std::cout << v1[0] << " " << v2[0] << std::endl; // Outputs: 1 10
}

Here, v1 and v2 have different buffers; changes in v2 do not affect v1.