I want to create n number element in an array. In the first input line I ask to give the number of elements, in the second line I ask for the actuall elements. I tried this code
int main() {
int first_line;
cin >> first_line;
int second[first_line];
cin>>second;
cout<< second;
return 0;
}
Input should look like
input
8
1 2 3 4 5 6 7 8
output
1 2 3 4 5 6 7 8
I need to the second line be in integer array.
An array (at least as it's defined in C++) simply can't do what you're asking for.
What you're really looking for is a std::vector, which does this quite nicely.
int main() {
int first_line;
cin >> first_line;
std::vector<int> second(first_line);
for (int i=0; i<first_line; i++) {
int temp;
cin>>temp;
second.push_back(temp);
}
for (auto i : second) {
cout<< i << ' ';
}
cout << "\n";
return 0;
}
First thing first you cannot use a variable length array in C++. So use a std::vector instead.
std::vector<int> second(first_line);
for reading you need to cin in a loop e.g. for loop.
The implementation left to the OP as a practice.
There are several collection types available in the C++ Standard Template Library, one of which std::vector<> will work just fine.
However if you want to use an array with straightforward array mechanics and syntax then an alternative would be to create your own array as in:
#include <iostream>
#include <memory>
int main() {
int first_line;
std::cin >> first_line;
int *second = new int[first_line]; // create an array, must manage pointer ourselves
// read in the element values
for (int i = 0; i < first_line; i++)
std::cin >> second[i];
// write out the element values with spaces as separators
for (int i = 0; i < first_line; i++)
std::cout << second[i] << " ";
delete [] second; // delete the array as no longer needed.
return 0;
}
Using std::unique_ptr<> to contain the pointer to the array would be more convenient and safer and just as easy to use. Create the array with std::unique_ptr<int[]> second( new int[first_line]); and then remove the no longer needed delete[]. std::unique_ptr[] will take care of deleting the array once it goes out of scope.
