USACO_2_2_Party Lamps

没什么特别的方法，c的大小不会影响到效率，最多仅有8种结果，我写了一个configuration类，每个configuration就是一种可能的结果

/**//*
ID: sdjllyh1
PROG: lamps
LANG: JAVA
complete date: 
complexity: 
author: LiuYongHui From GuiZhou University Of China
more article: www.cnblogs.com/sdjls
*/

import java.io.*;
import java.util.*;

public class lamps
{
    private static int n, c;
    private static int[] mustBeOn;
    private static int[] mustBeOff;
    private static ArrayList configurations = new ArrayList();

    public static void main(String[] args) throws IOException
    {
        init();
        run();
        output();
        System.exit(0);
    }

    private static void run()
    {
        configuration conf;

        if (c==0)
        {
            conf = new configuration(n);
            if (isConsistent(conf))
            {
                configurations.add(conf);
            }
        }
        else if(c==1)
        {
            conf = new configuration(n);
            conf.pressButton1();
            if (isConsistent(conf))
            {
                configurations.add(conf);
            }

            conf= new configuration(n);
            conf.pressButton2();
            if (isConsistent(conf))
            {
                configurations.add(conf);
            }

            conf= new configuration(n);
            conf.pressButton3();
            if (isConsistent(conf))
            {
                configurations.add(conf);
            }

            conf= new configuration(n);
            conf.pressButton4();
            if (isConsistent(conf))
            {
                configurations.add(conf);
            }
        }
        else 
        {
            conf= new configuration(n);
            conf.pressButton2();
            conf.pressButton3();
            if (isConsistent(conf))
            {
                configurations.add(conf);
            }

            conf= new configuration(n);
            conf.pressButton1();
            conf.pressButton3();
            if (isConsistent(conf))
            {
                configurations.add(conf);
            }

            conf= new configuration(n);
            conf.pressButton1();
            conf.pressButton2();
            if (isConsistent(conf))
            {
                configurations.add(conf);
            }

            conf= new configuration(n);
            conf.pressButton1();
            conf.pressButton4();
            if (isConsistent(conf))
            {
                configurations.add(conf);
            }

            conf= new configuration(n);
            conf.pressButton2();
            conf.pressButton4();
            if (isConsistent(conf))
            {
                configurations.add(conf);
            }

            conf= new configuration(n);
            conf.pressButton3();
            conf.pressButton4();
            if (isConsistent(conf))
            {
                configurations.add(conf);
            }

            conf = new configuration(n);
            conf.pressButton4();
            if (isConsistent(conf))
            {
                configurations.add(conf);
            }

            conf = new configuration(n);
            if (isConsistent(conf))
            {
                configurations.add(conf);
            }
        }

        Collections.sort(configurations);
        deleteRepetition();
    }

    private static boolean isConsistent(configuration value)
    {
        for (int i = 0; i < mustBeOn.length; i++)
        {
            if (!value.isOn[mustBeOn[i]])
            {
                return false;
            }
        }

        for (int i = 0; i < mustBeOff.length; i++)
        {
            if (value.isOn[mustBeOff[i]])
            {
                return false;
            }
        }

        return true;
    }

    // call must be after sort
    private static void deleteRepetition()
    {
        int i=0;
        while (i+1<configurations.size())
        {
            configuration cLeft=(configuration)configurations.get(i);
            configuration cRight=(configuration)configurations.get(i+1);
            if (cLeft.compareTo(cRight) == 0)
            {
                configurations.remove(i + 1);
            }
            else
            {
                i++;
            }
        }
    }

    private static void init() throws IOException
    {
        BufferedReader f = new BufferedReader(new FileReader("lamps.in"));
        n = Integer.parseInt(f.readLine());
        c = Integer.parseInt(f.readLine());

        int[] tmpMustBeON = new int[n];
        int[] tmpMustBeOff = new int[n];
        int mustBeOnCounter = 0;
        int mustBeOffCounter = 0;

        StringTokenizer st = new StringTokenizer(f.readLine());
        int readNumber = Integer.parseInt(st.nextToken());
        while (readNumber != -1)
        {
            tmpMustBeON[mustBeOnCounter] = readNumber - 1;
            mustBeOnCounter++;
            readNumber = Integer.parseInt(st.nextToken());
        }

        st = new StringTokenizer(f.readLine());
        readNumber = Integer.parseInt(st.nextToken());
        while (readNumber != -1)
        {
            tmpMustBeOff[mustBeOffCounter] = readNumber - 1;
            mustBeOffCounter++;
            readNumber = Integer.parseInt(st.nextToken());
        }
        f.close();

        mustBeOn = new int[mustBeOnCounter];
        mustBeOff = new int[mustBeOffCounter];
        System.arraycopy(tmpMustBeON, 0, mustBeOn, 0, mustBeOnCounter);
        System.arraycopy(tmpMustBeOff, 0, mustBeOff, 0, mustBeOffCounter);
    }

    private static void output() throws IOException
    {
        PrintWriter out = new PrintWriter(new BufferedWriter(new FileWriter("lamps.out")));
        Iterator it = configurations.iterator();
        if (it.hasNext())
        {
            while (it.hasNext())
            {
                out.println(it.next());
            }
        }
        else
        {
            out.println("IMPOSSIBLE");
        }
        out.close();
    }
}

class configuration implements Comparable
{
    public boolean[] isOn;
    public int length;

    public configuration(int size)
    {
        this.length = size;
        this.isOn = new boolean[length];
        Arrays.fill(isOn, true);
    }

    public int compareTo(Object arg0)
    {
        configuration compareObject = (configuration)arg0;

        for (int i = 0; i < this.length; i++)
        {
            if (this.isOn[i] && !compareObject.isOn[i])
            {
                return 1;
            }
            if (!this.isOn[i] && compareObject.isOn[i])
            {
                return -1;
            }
        }
        return 0;
    }

    public void pressButton1()
    {
        for (int i = 0; i < this.length; i++)
        {
            isOn[i] = !isOn[i];
        }
    }

    public void pressButton2()
    {
        int i = 0;
        while (i < this.length)
        {
            isOn[i] = !isOn[i];
            i += 2;
        }
    }

    public void pressButton3()
    {
        int i = 1;
        while (i < this.length)
        {
            isOn[i] = !isOn[i];
            i += 2;
        }
    }

    public void pressButton4()
    {
        int i = 0;
        while (i < this.length)
        {
            isOn[i] = !isOn[i];
            i += 3;
        }
    }

    public String toString()
    {
        StringBuffer retStr = new StringBuffer();
        for (int i = 0; i < this.length; i++)
        {
            if (isOn[i])
            {
                retStr.append("1");
            }
            else
            {
                retStr.append("0");
            }
        }
        return retStr.toString();
    }
}