Codercharts:Word Lazy swap

gistfile1.java

import java.io.*;
import java.util.*;
public class word_lazy_swap 
{
	public static HashSet<String>dict;
	public static void main(String[] args) throws Exception 
	{
		InputReader sc=new InputReader(new FileInputStream(args[0]));
		dict=new HashSet<String>();
		while(!sc.isExhausted()) dict.add(sc.readLine());
		Queue<String>q=new LinkedList<String>();
		sc=new InputReader(new FileInputStream(args[1]));
		String st="",end="",cur="";
		Set<String>used=new LinkedHashSet<String>();
		HashMap<String,String>back=new HashMap<String,String>();
		int flag=0,res=0;
		List<String>suc;
		while(!sc.isExhausted())
		{
			st=sc.readString();
			end=sc.readString();
			q.add(st);
			while(!q.isEmpty())
			{
				cur=q.remove();
				suc=successors(cur);
				for(int i=0;i<suc.size();i++)
				{
					if(cur.equals(end))
					{
						flag=1;
						break;
					}
					else
					{
						if(!used.contains(suc.get(i))&&!q.contains(suc.get(i)))
						{
							q.add(suc.get(i));
							back.put(suc.get(i),cur);
							used.add(cur);
						}		
					}
				}
				if(flag==1) break;
			}
			cur=end;
			while(back.get(cur)!=null)
			{
				cur=back.get(cur);
				res++;
			}
			res++;
			System.out.println(res);
			used.clear();
			back.clear();
			q.clear();
			res=0;flag=0;
		}
  	}
  	public static LinkedList<String>successors(String cur)
  	{
  		StringBuffer sb;
  		LinkedList<String>suc=new LinkedList<String>();
  		int n=cur.length();
  		char ch;
  		for(int i=0;i<n;i++)
  		{
  			sb=new StringBuffer(cur);
  			ch=sb.charAt(i);
  			for(char j='A';j<='Z';j++)
  			{
				if(ch!=j)
				{
  					sb.setCharAt(i,j);
  					if(dict.contains(sb.toString())) suc.add(sb.toString());
  					sb.setCharAt(i,ch);
				}
  			}
  		}
  		return suc;
  	}
}

class InputReader {
	private boolean finished = false;
	private InputStream stream;
	private byte[] buf = new byte[1024];
	private int curChar;
	private int numChars;

	public InputReader(InputStream stream) {
		this.stream = stream;
	}

	public int read() {
		if (numChars == -1)
			throw new InputMismatchException();
		if (curChar >= numChars) {
			curChar = 0;
			try {
				numChars = stream.read(buf);
			} catch (IOException e) {
				throw new InputMismatchException();
			}
			if (numChars <= 0)
				return -1;
		}
		return buf[curChar++];
	}

	public int peek() {
		if (numChars == -1)
			return -1;
		if (curChar >= numChars) {
			curChar = 0;
			try {
				numChars = stream.read(buf);
			} catch (IOException e) {
				return -1;
			}
			if (numChars <= 0)
				return -1;
		}
		return buf[curChar];
	}

	public String readString() {
		int c = read();
		while (isSpaceChar(c))
			c = read();
		StringBuffer res = new StringBuffer();
		do {
			res.appendCodePoint(c);
			c = read();
		} while (!isSpaceChar(c));
		return res.toString();
	}

	private boolean isSpaceChar(int c) {
		return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
	}

	private String readLine0() {
		StringBuffer buf = new StringBuffer();
		int c = read();
		while (c != '\n' && c != -1) {
			if (c != '\r')
				buf.appendCodePoint(c);
			c = read();
		}
		return buf.toString();
	}

	public String readLine() {
		String s = readLine0();
		while (s.trim().length() == 0)
			s = readLine0();
		return s;
	}

	public String readLine(boolean ignoreEmptyLines) {
		if (ignoreEmptyLines)
			return readLine();
		else
			return readLine0();
	}

	public char readCharacter() {
		int c = read();
		while (isSpaceChar(c))
			c = read();
		return (char) c;
	}

	public boolean isExhausted() {
		int value;
		while (isSpaceChar(value = peek()) && value != -1)
			read();
		return value == -1;
	}

	public String next() {
		return readString();
	}
}