全排列算法 java 实现

LoveBNU 小六 WangBNU — Wed, 21 Sep 2005 05:27:00 GMT

  1  /*
  2  * Created on Oct 22, 2004
  3  *
  4  * To change the template for this generated file go to
  5  * Window>Preferences>Java>Code Generation>Code and Comments
  6  */
  7
  8 /**
  9  * @author WangBNU helloquota@163.com My Homepage http://bnulinux.yeah.net To
10  *         change the template for this generated type comment go to
11  *         Window>Preferences>Java>Code Generation>Code and Comments
12  */
13 public class PaiLie {
14     public static void main(String args[]) {
15         int leng = args[0].length();
16         int[] a = new int[leng];
17         boolean[] c = new boolean[leng];
18         for (int i = 0; i < leng; i++) {
19             a[i] = i + 1;
20             c[i] = false;
21         }
22         int ii = findActiveM(a, c);
23
24         for (int i = 0; i < args[0].length(); i++)
25             System.out.print(a[i]);
26         System.out.println();
27
28         if (ii >= 0) {
29             do {
30                 int activeM = a[ii];
31                 if (c[ii] == false) {
32                     swapInt(a, ii, ii - 1);
33                     swapBoolean(c, ii, ii - 1);
34                 } else {
35                     swapInt(a, ii, ii + 1);
36                     swapBoolean(c, ii, ii + 1);
37                 }
38                 for (int i = 0; i < args[0].length(); i++) {
39                     System.out.print(a[i]);
40                     if (a[i] > activeM)
41                         c[i] = !c[i];
42                 }
43                 System.out.println();
44                 ii = findActiveM(a, c);
45
46             } while (ii >= 0);
47         }
48     }
49
50     /**
51      * @param aa
52      *
53      * @param a
54      * @param b
55      */
56     private static void swapInt(int[] aa, int a, int b) {
57         int temp = aa[a];
58         aa[a] = aa[b];
59         aa[b] = temp;
60     }
61
62     private static void swapBoolean(boolean[] aa, int a, int b) {
63         boolean temp = aa[a];
64         aa[a] = aa[b];
65         aa[b] = temp;
66     }
67
68     private static int findActiveM(int[] a, boolean[] c) {
69
70         int first1 = 0, first2 = 0;
71         int m = -1, n = -1;
72         for (int i = 1; i < a.length - 1; i++) {
73             if (c[i] == false) {
74                 if ((a[i] > a[i - 1]) && a[i] > first1) {
75                     first1 = a[i];
76                     m = i;
77                 }
78             } else {
79                 if ((a[i] > a[i + 1]) && a[i] > first2) {
80                     first2 = a[i];
81                     n = i;
82                 }
83             }
84         }
85         if ((c[0] == true) && (a[0] > a[1]) && (a[0] > first2)) {
86             first2 = a[0];
87             n = 0;
88         }
89         if ((c[a.length - 1] == false) && (a.length > 1)
90                 && (a[a.length - 1] > a[a.length - 2])
91                 && (a[a.length - 1] > first1)) {
92             first1 = a[a.length - 1];
93             m = a.length - 1;
94         }
95         if (first1 >= first2)
96             return m;
97         else
98             return n;
99     }
100
101 }
102

LoveBNU 小六 WangBNU 2005-09-21 13:27 发表评论

输出一个集合所有冪集的代码

LoveBNU 小六 WangBNU — Tue, 13 Sep 2005 03:07:00 GMT

public String[] getAll(int[] array) {
        int n = Array.getLength(array);
        int total = (int) Math.pow(2, n);
        Logger log = Logger.getLogger("myLog");
        log.info(" the  total :" + total);
        String[] outArray = new String[total];
        for (int i = 0; i < total; i++) {
            StringBuffer bs = new StringBuffer("");
            for (int j = 0; j < n; j++) {
                if (((i >> j) % 2) == 1) {
                    bs.append(String.valueOf(Array.get(array, j)));
                }
            }
            outArray[i] = bs.toString();
        }
        return outArray;
    }

以上代码把生成的子集存放到一个字符串数组中,当集合的基数很大时,需要很大内存, 可以根据需要把上面程序改改不要放到数组中,而是边生成边使用.

LoveBNU 小六 WangBNU 2005-09-13 11:07 发表评论

BlogJava-★★★★★ 龙门乱弹 ★★★★★-随笔分类-算法之妙

全排列算法 java 实现

输出一个集合所有冪集的代码