如何在C++中声明一个用变量初始化的数组

Question

I know this sound easy to you guys but I think this may be different

Here is my simple code in which i am getting error in declaring Array

#include<iostream>
using namespace std;

int top=-1,capacity=2;
int arr[capacity];

main(){
}//main

Answer 1

A fixed length array needs a compile-time constant to declare its size. You need to declare capacity as const or constexpr in order to use it in an array declaration, eg:

#include <iostream>
using namespace std;

int top = -1;
const int capacity = 2;
int arr[capacity];

main(){
}

If you want to define the capacity at runtime then you need to use a dynamic array, like std::vector , eg:

#include <iostream>
#include <vector>
using namespace std;

int top = -1, capacity;
vector<int> arr;

main(){
    capacity = ...;
    arr.resize(capacity);
}