Interview Street Challenges - Picking_cards

Picking_cards.java

package interviewstreet;

import java.util.HashMap;
import java.util.Scanner;

public class Picking_cards {

	int num;
	int[] card_nums;
	HashMap<Integer,Integer> hm=new HashMap<Integer,Integer>();
	public Picking_cards(int num_of_cards, int[] cards) {
		this.num=num_of_cards;
		this.card_nums=cards;
	}

	public long solve()
	{
		int buf=0;
		long ret=0;
		for(int i=0;i<num;i++)
		{
			int key=card_nums[i];
			if(this.hm.containsKey(key))
			{
				int value=this.hm.get(key);
				this.hm.put(key, ++value);
			}
			else
			{
				this.hm.put(key, 1);
			}
		}
		if(hm.containsKey(0))
		{
			for(int key:hm.keySet())
			{
				if(buf==0)
				{
					ret=fact(hm.get(key));
					buf++;
				}
				else if(ret>=hm.get(key))
				{
					ret*=fact(hm.get(key));
					buf++;
				}
			}
		}
		if(hm.size()!=buf)
		{
			ret=0;
		}
		return ret;
	}
	public long fact(Integer fc)
	{
		long ret=1;
		for(int i=1;i<=fc;i++)
		{
			ret*=i;
		}
		return ret;
	}
	public static void main(String args[])
	{
		Scanner scanner = new Scanner(System.in);
		 int no_cases = scanner.nextInt();
			for (int i = 0; i < no_cases; i++) {
				int num_of_cards = scanner.nextInt();
				int[] cards=new int[num_of_cards];
				for(int j=0;j<num_of_cards;j++)
				{
					cards[j]=scanner.nextInt();
				}
				Picking_cards pc =new Picking_cards(num_of_cards,cards);
				System.out.println(pc.solve());
			}
	}
}