How to save a specific column into an array in C++?

I assume the user enters the coumn number over the console. So you can use the built-in cin function to read the input. You can use for loop and string streams to get the values. Code below; although you may have tweek it a little bit as per your needs

Edit: The code below has been edited a little bit. Now it should answer your question.

#include <iostream>
#include <fstream>
#include <string>
using namespace std;
int main()
{
   int n;
   cin >>n; //user needs to input the column number
   fstream newfile;
   //newfile.open("file.txt",ios::out);  // open the file to perform write operation using file object; Activate this function if you want to overwrite
   newfile.open("file.txt",ios::in); //open the file to perform read operation using file object
   if (newfile.is_open())
   {
      string line;
      getline(newfile, line); //skipping the first line
      while(getline(newfile, line))//loop throuhg rest of the lines
      { 
            int temp=n;
            while(temp != 0)//loop until you get to the requied column
            {
                getline(newfile, line, '\t'); //get the vaue separted by tab='\t'. Be sure that the last column also ends in '\t'
                temp--;
            }
            cout<<line<<endl; //now line holds the element on the loop-row of the selected column
      }
      newfile.close(); //close the file object.
   }
}