poj 1129 Channel Allocation

http://poj.org/problem?id=1129

import java.util.*;
import java.math.*;
public class Main {
    public static boolean flag=false;
    public static int ans=0;
    public static void main(String []args)
    {
        Scanner cin=new Scanner(System.in);
        int n;
        String str;
        while(cin.hasNext())
        {
            ans=1;
            int [][]g=new int[100][100];
            int []hash=new int[100];
             n=cin.nextInt();
             if(n==0) break;
             for(int i=0; i<n; i++)
             {
                 str=cin.next();
                 for(int j=2; j<(int)str.length(); j++)
                 {
                     g[str.charAt(0)-'A'][str.charAt(j)-'A']=1;
                 }
             }
             flag=false;
             dfs(0,1,g,n,hash);
             if(ans==1)
             {
             System.out.println("1 channel needed.");
             }
             else
             {
                 System.out.println(ans+" channels needed.");
             }
        }
    }
    public static int deal(int id,int co,int n,int g[][],int hash[])
    {
        for(int i=0; i<n; i++)
        {
            if(g[id][i]==1&&co==hash[i])
            {
                return 0;
            }
        }
        return 1;
    }
    public static void dfs(int num,int m1,int g[][],int n,int hash[])
    {
        if(flag) return;
        if(num>=n)
        {
            flag=true;
            return;
        }
        for(int i=1; i<=m1; i++)
        {
            if(deal(num,i,n,g,hash)==1)
            {
                hash[num]=i;
                dfs(num+1,m1,g,n,hash);
                hash[num]=0;
            }
        }
        if(flag==false)
        {
            ans++;
            dfs(num,m1+1,g,n,hash);
        }
    }
}