/**
 *  This program illustrates reading data from a file into parallel
 *  arrays for later processing.   It does some unnecessary things,
 *  and inefficiently too.  (Can you identify those inefficiencies?)
 *
 *  The program opens the input file, reads in the integer n, then
 *  reads a list of n student records, where each record consists of
 *  these four fields, separated by whitespace:
 *      - first name
 *      - last name
 *      - login name for email address
 *      - which section they're in.
 *  The program then prints out a list of login names of students
 *  in Sections 3 and 4.
 *
 *  To compile, type
 *      kotlinc Students.kt
 *  To run using [stduentsData.txt] as input file, type
 *      kotlin StudentsKt studentsData.txt
 *  and you should get the following output:
 *
 *  Section 3
 *  ---------
 *  swang
 *  ataylor
 *  rallen
 *  rayyangar
 *  ...
 *
 *  Section 4
 *  ---------
 *  drosner
 *  dbarret
 *  ecapra
 *  pcombs
 *  ...
 *
 */

fun main(args: Array<String>) { 
    val file = java.io.FileReader(args[0])
    val scanner = java.util.Scanner(file)

    // read the number of students
    val n = scanner.nextInt()

    // initialize four parallel arrays
    val first = Array<String>(n) { "" }
    val last = Array<String>(n) { "" }
    val login = Array<String>(n) { "" }
    val section = IntArray(n)

    // read in the data
    for (i in 0 until n) {
        first[i] = scanner.next()
        last[i] = scanner.next()
        login[i] = scanner.next()
        section[i] = scanner.nextInt()
    }

    // print login names of all students in section 3
    println("""Section 3
              |---------
        """.trimMargin())
    for (i in 0 until n) {
        if (section[i] == 3)
            println(login[i])
    }
    println()

    // print login names of all students in section 4
    println("""Section 4
              |---------
        """.trimMargin())
    for (i in 0 until n) {
        if (section[i] == 4) {
            println(login[i])
        }
    }

    scanner.close()
    file.close()
}