Hackerrank - Picking Cards

Problem Statement
A description of the problem can be found on Hackerrank.

Solution
Sort the array descending. Take N from the input.
For each element e substract N - e. That means that there is only N - e combinations to choose these two cards. After substraction decrement N and select the next element. All card combinations are multiplication of all N - e substractions. If at least N - e is lower than 0 the result is automatically 0. Don’t forget modulo 1 000 000 007.

I created solution in:

Java
JavaScript
Scala
Ruby

All solutions are also available on my GitHub.

Java

import java.util.*;

public class PickingCards {

    public static void main(String[] args) {
        Scanner stdin = new Scanner(System.in);
        int tests = stdin.nextInt();
        for(int i = 0; i < tests; i++) {
            int length = stdin.nextInt();
            long[] arr = new long[length];
            for(int j = 0; j < arr.length; j++) {
                arr[j] = stdin.nextLong();
            }
            Arrays.sort(arr);
            long result = 1;
            for (int j = arr.length - 1; j >= 0; j--) {
                long diff = length - arr[j];
                if (diff < 0) diff = 0;
                result *= diff;
                result %= 1000000007;
                length -= 1;
            }
            System.out.println(result);
        }
        stdin.close();
    }
}

import java.util.*;

public class PickingCards {

public static void main(String[] args) {

Scanner stdin = new Scanner(System.in);

int tests = stdin.nextInt();

for(int i = 0; i < tests; i++) {

int length = stdin.nextInt();

long[] arr = new long[length];

for(int j = 0; j < arr.length; j++) {

arr[j] = stdin.nextLong();

}

Arrays.sort(arr);

long result = 1;

for (int j = arr.length - 1; j >= 0; j--) {

long diff = length - arr[j];

if (diff < 0) diff = 0;

result *= diff;

result %= 1000000007;

length -= 1;

}

System.out.println(result);

}

stdin.close();

}

JavaScript

'use strict';

const processData = input => {
    let lines = input.split("\n");
    let tests = parseInt(lines[0]);
    let index = 1;
    for (let i = 0; i < tests; i++) {
        let length = parseInt(lines[index++]);
        let arr = lines[index++].split(" ").map(i => parseInt(i)).sort((a, b) => a - b);
        let result = 1;
        for (let j = arr.length - 1; j >= 0; j--) {
            let diff = length - arr[j];
            if (diff < 0) diff = 0;
            result *= diff;
            result %= 1000000007;
            length -= 1;
        }
        console.log(result);
    }
};

process.stdin.resume();
process.stdin.setEncoding("ascii");

var _input = "";
process.stdin.on("data", input => _input += input);
process.stdin.on("end", () => processData(_input));

'use strict';

const processData = input => {

let lines = input.split("\n");

let tests = parseInt(lines[0]);

let index = 1;

for (let i = 0; i < tests; i++) {

let length = parseInt(lines[index++]);

let arr = lines[index++].split(" ").map(i => parseInt(i)).sort((a, b) => a - b);

let result = 1;

for (let j = arr.length - 1; j >= 0; j--) {

let diff = length - arr[j];

if (diff < 0) diff = 0;

result *= diff;

result %= 1000000007;

length -= 1;

}

console.log(result);

}

};

process.stdin.resume();

process.stdin.setEncoding("ascii");

var _input = "";

process.stdin.on("data", input => _input += input);

process.stdin.on("end", () => processData(_input));

Scala

import scala.io.Source

object PickingCards extends App {
  val lines = Source.stdin.getLines()
  val cards = lines.drop(1).filter(_.contains(" "))
  cards.foreach(line => {
    println(pickingCombinations(line))
  })

  def pickingCombinations(s: String): Long = {
    val arr = s.split(" ").map(_.toLong).sorted
    val arrLength = arr.length
    picks(arr, arrLength, 1)
  }

  def picks(list: Array[Long], l: Int, combinations: Long): Long = {
    if(l == 0) {
      return combinations
    }
    val diff = l - list(l - 1)
    val normalizedDiff = if (diff > 0) diff else 0
    val newCombinations = (combinations * normalizedDiff) % 1000000007
    picks(list, l - 1, newCombinations)
  }
}

import scala.io.Source

object PickingCards extends App {

val lines = Source.stdin.getLines()

val cards = lines.drop(1).filter(_.contains(" "))

cards.foreach(line => {

println(pickingCombinations(line))

})

def pickingCombinations(s: String): Long = {

val arr = s.split(" ").map(_.toLong).sorted

val arrLength = arr.length

picks(arr, arrLength, 1)

}

def picks(list: Array[Long], l: Int, combinations: Long): Long = {

if(l == 0) {

return combinations

}

val diff = l - list(l - 1)

val normalizedDiff = if (diff > 0) diff else 0

val newCombinations = (combinations * normalizedDiff) % 1000000007

picks(list, l - 1, newCombinations)

}

Ruby

test_cases = gets.chomp.to_i
test_cases.times do
  array_length = gets.chomp.to_i
  array  = gets.chomp.split.map { |e| e.to_i }
  
  array.sort! { |i,j| j <=> i }
  
  result = 1
  array.each do |element|
    diff = array_length - element
    diff = 0 if diff < 0
    result *= diff
    result %= 1000000007
    array_length -= 1
  end
  puts result
end

test_cases = gets.chomp.to_i

test_cases.times do

array_length = gets.chomp.to_i

array = gets.chomp.split.map { |e| e.to_i }

array.sort! { |i,j| j <=> i }

result = 1

array.each do |element|

diff = array_length - element

diff = 0 if diff < 0

result *= diff

result %= 1000000007

array_length -= 1

end

puts result

end

Pavol Pidanič

I can count to 1023 with 10 fingers

Hackerrank – Picking Cards