Scala constructing a "List", read from stdin, output to stdout

Question

I'm trying to read formatted inputs from stdin using Scala:

The equivalent C++ code is here:

int main() {
  int t, n, m, p;
  cin >> t;
  for (int i = 0; i < t; ++i) {
    cin >> n >> m >> p;
    vector<Player> players;
    for (int j = 0; j < n; ++j) {
      Player player;
      cin >> player.name >> player.pct >> player.height;
      players.push_back(player);
    }
    vector<Player> ret = Solve(players, n, m, p);
    cout << "Case #" << i + 1 << ": ";
    for (auto &item : ret) cout << item.name << " ";
    cout << endl;
  }
  return 0;
}

Where in the Scala code, I'd like to Use

players: List[Player], n: Int, m: Int, p: Int

to store these data.

Could someone provide a sample code?

Or, just let me know how to:

how the "main()" function work in scala
read formatted text from stdin
efficiently constructing a list from inputs (as list are immutable, perhaps there's a more efficient way to construct it? rather than having a new list as each element comes in?)
output formatted text to stdout

Thanks!!!

Regarding reading/parsing binary data I recommend to look here: stackoverflow.com/questions/2667714/… — dmitry
– dmitry, Commented Nov 26, 2013 at 12:10
1. and 4. look on Google 2. java.util.Scanner 3. basically, ListBuffer, assuming you're using imperative style, which is probably best for this type of thing. Otherwise (since you tagged this "functional-programming"), you can use folds or recursion. However Vector may be more suitable than List if you're appending. — Luigi Plinge
– Luigi Plinge, Commented Nov 26, 2013 at 16:09

Marth · Accepted Answer · 2013-11-26 10:32:57Z

1

I don't know C++, but something like this should work :

def main(args: Array[String]) = {
    val lines = io.Source.stdin.getLines
    val t = lines.next.toInt
    // 1 to t because of ++i
    // 0 until t for i++
    for (i <- 1 to t) {
      // assuming n,m and p are all on the same line
      val Array(n,m,p) = lines.next.split(' ').map(_.toInt)
      // or (0 until n).toList if you prefer
      // not sure about the difference performance-wise
      val players = List.range(0,n).map { j =>
        val Array(name,pct,height) = lines.next.split(' ')
        Player(name, pct.toInt, height.toInt)
      }
      val ret = solve(players,n,m,p)
      print(s"Case #${i+1} : ")
      ret.foreach(player => print(player.name+" "))
      println
    }
  }

answered Nov 26, 2013 at 10:32

Marth

24.9k3 gold badges68 silver badges76 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

loloof64 Over a year ago

If you define a subclass of Application, then you don't need to define a main method, and you can code as a script directly in the curly braces.

Collectives™ on Stack Overflow

Scala constructing a "List", read from stdin, output to stdout

1 Answer 1

1 Comment

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Linked

Related