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  1. Practice
  2. C++
  3. Introduction
  4. Arrays Introduction
  5. Discussions

Arrays Introduction

  • thebartman + 5 comments

    I'm trying to get better with the STL. Here's what I came up with. I just ignored the first line of input.

    #include <vector>
#include <iostream>
#include <algorithm>
#include <iterator>

int main() {
    std::cin.ignore(256, '\n');
    std::vector<int> v;
    std::copy(std::istream_iterator<int> (std::cin), std::istream_iterator<int> (), back_inserter(v));
    std::copy(v.rbegin(), v.rend(), std::ostream_iterator<int> (std::cout, " "));

    return 0;
}
    • ronnie_c995 + 2 comments

      Since you are practising getting better, it's better style in c++14 to use copy(rbegin(v),rend(v),ostream_iterator(std::cout," "));

      • thebartman + 0 comments

        Oops, yup, always forget to do that. Thank you!

      • SmittyMcSmith + 1 comment

        why is this better style? rbegin/rend are methods in the vector's class... why wouldn't you call them as he originally wrote?

        • ronnie_c995 + 0 comments

          Because begin(), end() functions (not methods) are standard and work for all containers and even arrays like char[]. They are specialized to work with any container you might write too as long as it follows certain guidelines.

    • vdeshmuk + 0 comments

      This is so concise. Love it!

    • SmittyMcSmith + 0 comments

      this will only terminate when the stream ends which doesn't happen with a carrage return... how would you modify this such that it itertively reads in till it hits a cr?

    • hmt905 + 0 comments

      why we use vector concept here.pelase explain

    • ptgrimes235 + 0 comments

      Similar solution, but only one call to copy (reverse copy) and utilizing the vector constructor instead.

      void flipInput(istream&, ostream&);

int main() {
    // Remove First Line
    cin.ignore(numeric_limits<streamsize>::max(), '\n');

    flipInput(cin, cout);

    return 0;
}

void flipInput(istream &in, ostream &out) {

    // Set up iterator over cin istream
    istream_iterator<int> input_begin(in);
    istream_iterator<int> input_end;

    // Set up iterator for cout ostream (space separation)
    ostream_iterator<int> output_begin(out, " ");

    // Reverse iterator not defined over istream (no -- operator)
    // Copy data with vector constructor
    vector<int> input_data(input_begin, input_end);

    // Reverse copy vector iterators, output to ostream iterator
    reverse_copy(input_data.begin(), input_data.end(), output_begin);
    
    return;
}