expression must have a constant value in c++

Question

So, I am creating an object that have an array as it's instance. The size of this array will determined by the client program. Later in my program, I have to create a temp array that have the same capacity as the instance variable. So, I put:

int temp[capacity];

However, when I try to compile it, it failed. It said that I have to have a fix value instead of putting capacity. Any idea how can I fix this problem? thx

Answer 1

You can only construct such an array if capacity is known at compile time. For dynamically sized arrays, use std::vector :

#include <vector>

std::vector<int> temp(capacity); // makes a vector with capacity elements

Answer 2

Instead of writing this:

int temp[capacity]

Just write:

int* temp = (int*)malloc(capacity);