fun countSort(arr: Array<Array<String>>): Unit {
    // Find the min and max values of the associated integers.
    //
    // Will be min=0 max=6 from the sample input.
    var min = Int.MAX_VALUE
    var max = Int.MIN_VALUE
    arr.forEach {
        val num = Integer.parseInt(it[0])
        if (num < min) min = num
        if (num > max) max = num
    }
    
    // Create a count array for counting occurrences of each
    // associated integer.
    // Note associated integers might not be 0-indexed so
	// work out minimum number of spaces required.
    //
    // From the sample: max - min + 1 = 6 - 0 + 1 = 7
    // An array of 7 items will fit each value count (0-6).
    val countArray = IntArray(max - min + 1)
    
    // Go through the input array and count how many occurrences
    // of each associated integer there are.
    //
    // From the sample this is:
	// 0=6, 1=2, 2=2, 3=1, 4=4, 5=1, 6=4
    arr.forEach { 
        val num = Integer.parseInt(it[0])
        countArray[num - min]++        
    }
    
    // Now update the count array to have running totals from left
    // to right.
    //
    // So add the first count to the second, the first 2 counts to
    // the third, and so on...
    //
    // From the sample this is:
    // 0=6, 1=8, 2=10, 3=11, 4=15, 5=16, 6=20
    for (index in 1 until countArray.size) {
        countArray[index] += countArray[index - 1]
    }
    
    // Create the output array. Note it's the same size as the
	// input.
    // Fill with dashes by default to save filling them later.
    val output = Array<String>(arr.size) { "-" }
    
    // This is where everything comes together.
    //
    // Loop the input array from the end to the middle. 
    // Start at the end to ensure order is retained (stability).
    // Finish in the middle as we're told to have dashes for the
    // first half.
    for (index in arr.size - 1 downTo arr.size / 2) {
        // Get the associated integer for the item.
        val num = Integer.parseInt(arr[index][0])
        
        // Calculate where the item goes in the output array.
        // This is done by looking in the countArray.
        //
        // Taking the sample input, the last item is [4, "the"].
        // So 4 - 0 - 1 = 3
        // countArray[3] is 11 (see above).
        val pos = countArray[num - min] - 1
        
        // Set position in the output array to the value.
        // Following the example [4, "the"] this will set position
        // 11 in the output array to "the".
        output[pos] = arr[index][1]
        
        // Decrease the count of the associated integer so next 
        // time the value is place in the correct place as we're
        // working backwards.
        countArray[num - min]--
    }
    
    // Print out the output array.
    output.forEach { 
        print("$it ")
    }
    println("")
}