hdu1.3.5 排列2

求4个数组成的全排列，第一个数字不能为0

思路：用字典序生成排列算法

代码如下

import java.io.FileInputStream;
import java.io.InputStreamReader;
import java.io.BufferedReader;
import java.io.PrintWriter;
import java.io.IOException;
import java.io.StreamTokenizer;
import java.util.Arrays;


public class Main{

    private StreamTokenizer cin;
    private PrintWriter cout;
    private static final boolean DEBUG = false;
    private static final int N = 4;
    private int[]  nums = new int[N];

    private void init()
    {
        try
        {
            if (DEBUG)
            {
                cin = new StreamTokenizer(new BufferedReader(new InputStreamReader(new FileInputStream("d:\\program\\intelj\\spoj\\src\\spoj.txt"))));
            }
            else
            {
                cin = new StreamTokenizer(new BufferedReader(new InputStreamReader(System.in)));
            }
            cout = new PrintWriter(System.out);
        }
        catch (IOException e)
        {
            e.printStackTrace();;
        }

    }

    private Integer next()
    {
        try
        {
            cin.nextToken();
            if (cin.ttype == StreamTokenizer.TT_EOF) return null;
            else if (cin.ttype == StreamTokenizer.TT_NUMBER) return (int)cin.nval;
            else return null;
        }
        catch(Exception e)
        {
            e.printStackTrace();
            return null;
        }
    }
    private boolean input()
    {
        Integer n = next();
        if (n == null) return false;

        nums[0] = n;
        for (int i = 1; i < N; i++)
        {
            n = next();
            nums[i] = n;
        }

        if (nums[0] == 0 && nums[1] == 0 && nums[2] == 0 && nums[3] == 0) return false;

        return true;
    }

    private void findMinPermutation()
    {
        int Min = 10;
        int j = 0;
        for (int i = 0; i < N; i++)
        {
            if (nums[i] != 0 && nums[i] < Min)
            {
                Min = nums[i];
                j = i;
            }
        }

        if (j != 0)
        {
            int tmp = nums[0]; nums[0] = nums[j]; nums[j] = tmp;
            Arrays.sort(nums, 1, N);
        }
    }

    private void print()
    {
        for (int i = 0; i < N; i++)
        {
            cout.print(nums[i]);
        }
    }

    private boolean nextPermutation()
    {
        int j = nums.length - 1;
        j--;
        while (!(j < 0 || nums[j] < nums[j + 1])) j--;
        if (j < 0)
        {
            return false;
        }

        int i = nums.length - 1;
        while (!(nums[j] < nums[i])) i--;
        int tmp = nums[i]; nums[i] = nums[j]; nums[j] = tmp;
        Arrays.sort(nums,j + 1, N);

        return true;
    }

    private void solve()
    {
        findMinPermutation();
        print();
        int pre = nums[0];
        while (nextPermutation())
        {
            int cur = nums[0];
            if (pre != cur)
            {
                cout.println();
            }
            else
            {
                cout.print(" ");
            }

            print();
            pre = cur;
        }
        cout.println();
        cout.flush();
    }

    public void run() {
        init();
        int cas = 0;
        while (input())
        {
            if (cas++ > 0) cout.println();
            solve();
        }
    }

    public static void main(String[] args)
    {
        new Main().run();
    }
}