我应该使用向量而不是数组吗？

Question

If I have a fixed number of elements of class MyClass, should I use arrays or vectors?, ie:

MyClass* myArray[];

or

std::vector<MyClass*> myVector;

?

Answer 1

Use std::array or raw arrays for a small, static number of elements.

If you have a lot of elements (more than say 100kb), you hog the stack and are asking for stack corruption / overflow. In that case, or if the number of elements can only be known at runtime, use std::vector .

Answer 2

if you know the number in compile time - use static array .

if the number is dynamic (obtained from the user) - vector is much better to save you the hurdle of managing the memory

Answer 3

"Fixed" has two meanings in this context. The usual one is set once, never change , such as a value read from input. This value is known at runtime and requires dynamic allocation on the heap. Your options are a C-style array with new or a vector; it is highly recommended you use a vector.

#include <vector>
#include <iostream>
int main() {
    int size;
    std::cin >> size;
    int *myArray = new int[size];
    std::vector<int> myVector(size);
}   

"Fixed" can also mean a compile-time constant , meaning it is constant for any run of the program. You can use a C-style array or a C++ array (automatic memory allocation on the stack).

#include <array>
int main() {
    const int size = 50;
    int myArray[size];
    std::array<int, size> myArray;
}

These are faster, but your program needs to have access to sufficient stack memory, which is something you can change in your project settings. See this topic for more info. If the size of the array is really big, you may want to consider allocating on the Heap anyway (vector).