Complete the Vec class, void reserve( int n ), void push_back( int v ),int at( int idx ). Complete this sample code to include the capacity and size, this in C++

#include

using namespace std;

class Vec { public: Vec() {

} int size() { return this->sz; }

int capacity() { return this->cap; }

void reserve( int n ) { // TODO: // (0) check the n should be > size, otherwise // ignore this action. if ( n > sz ) { // (1) create a new int array which size is n // and get its address int *newarr = new int[n]; // (2) use for loop to copy the old array to the // new array

// (3) update the variable to the new address

// (4) delete old array delete[] oldarr;

}

}

void push_back( int v ) { // TODO:

if ( sz == cap ) { cap *= 2; reserve(cap); }

// complete others

}

int at( int idx ) {

}

private: int *arr; int sz = 0; int cap = 0;

};

int main() { Vec v; v.reserve(10); v.push_back(3); v.push_back(2); cout << v.size() << endl; // 2 cout << v.capacity() << endl; // 10 v.push_back(3); v.push_back(2); v.push_back(3); v.push_back(4); v.push_back(3); v.push_back(7); v.push_back(3); v.push_back(8); v.push_back(2); cout << v.size() << endl; // 11 cout << v.capacity() << endl; // 20

for ( int i = 0; i < v.size(); i++ ) { cout << v.at(i) << endl; }

return 0; }