一.代码实现
1 package zhen;
2
3 import java.util.Arrays;
4
5 public class Arrangement {
6
7 /**
8 * 计算阶乘数，即n! = n * (n-1) * ... * 2 * 1
9 */
10 private static long factorial(int n) {
11 long sum = 1;
12 while( n > 0 ) {
13 sum = sum * n--;
14 }
15 return sum;
16 }
17
18 /**
19 * 排列计算公式A = n!/(n - m)!
20 */
21 public static long arrangement(int m, int n) {
22 return m <= n ? factorial(n) / factorial(n - m) : 0;
23 }
24
25 /**
26 * 排列选择（从列表中选择n个排列）
27 * @param dataList 待选列表
28 * @param n 选择个数
29 */
30 public static void arrangementSelect(String[] dataList, int n) {
31 System.out.println(String.format("A(%d, %d) = %d", dataList.length, n, arrangement(n, dataList.length)));
32 arrangementSelect(dataList, new String[n], 0);
33 }
34
35 /**
36 * 排列选择
37 * @param dataList 待选列表
38 * @param resultList 前面（resultIndex-1）个的排列结果
39 * @param resultIndex 选择索引，从0开始
40 */
41 private static void arrangementSelect(String[] dataList, String[] resultList, int resultIndex) {
42 int resultLen = resultList.length;
43 if(resultIndex >= resultLen) { // 全部选择完时，输出排列结果
44 System.out.println(Arrays.asList(resultList));
45 return;
46 }
47
48 // 递归选择下一个
49 for(int i = 0; i < dataList.length; i++) {
50 // 判断待选项是否存在于排列结果中
51 boolean exists = false;
52 for (int j = 0; j < resultIndex; j++) {
53 if (dataList[i].equals(resultList[j])) {
54 exists = true;
55 break;
56 }
57 }
58 if (!exists) { // 排列结果不存在该项，才可选择
59 resultList[resultIndex] = dataList[i];
60 arrangementSelect(dataList, resultList, resultIndex + 1);
61 }
62 }
63 }
64
65 /**
66 * 组合计算公式C<sup>m</sup><sub>n</sub> = n! / (m! * (n - m)!)
67 * @param m
68 * @param n
69 * @return
70 */
71 public static long combination(int m, int n) {
72 return m <= n ? factorial(n) / (factorial(m) * factorial((n - m))) : 0;
73 }
74
75 /**
76 * 组合选择（从列表中选择n个组合）
77 * @param dataList 待选列表
78 * @param n 选择个数
79 */
80 public static void combinationSelect(String[] dataList, int n) {
81 System.out.println(String.format("C(%d, %d) = %d", dataList.length, n, combination(n, dataList.length)));
82 combinationSelect(dataList, 0, new String[n], 0);
83 }
84
85 /**
86 * 组合选择
87 * @param dataList 待选列表
88 * @param dataIndex 待选开始索引
89 * @param resultList 前面（resultIndex-1）个的组合结果
90 * @param resultIndex 选择索引，从0开始
91 */
92 private static void combinationSelect(String[] dataList, int dataIndex, String[] resultList, int resultIndex) {
93 int resultLen = resultList.length;
94 int resultCount = resultIndex + 1;
95 if (resultCount > resultLen) { // 全部选择完时，输出组合结果
96 System.out.println(Arrays.asList(resultList));
97 return;
98 }
99
100 // 递归选择下一个
101 for (int i = dataIndex; i < dataList.length + resultCount - resultLen; i++) {
102 resultList[resultIndex] = dataList[i];
103 combinationSelect(dataList, i + 1, resultList, resultIndex + 1);
104 }
105 }
106
107 public static void main(String[] args) {
108 String[] array = new String[4];
109
110 array[0] = "SG614111010000000010001";
111 array[1] = "SG614111020000000020001";
112 array[2] = "SG614111030000000030001";
113 array[3] = "SG614111040000000040001";
114 /**
115 * 测试排列
116 */
117 System.out.println("测试排列：");
118 arrangementSelect(array, array.length);
119
120 /**
121 * 测试组合
122 */
123 System.out.println("测试组合：");
124 for(int i = 1; i <= array.length; i++){
125 combinationSelect(array, i);
126 }
127 }
128 }
二.结果
1 测试排列： 2 A(4, 4) = 24 3 [SG614111010000000010001, SG614111020000000020001, SG614111030000000030001, SG614111040000000040001] 4 [SG614111010000000010001, SG614111020000000020001, SG614111040000000040001, SG614111030000000030001] 5 [SG614111010000000010001, SG614111030000000030001, SG614111020000000020001, SG614111040000000040001] 6 [SG614111010000000010001, SG614111030000000030001, SG614111040000000040001, SG614111020000000020001] 7 [SG614111010000000010001, SG614111040000000040001, SG614111020000000020001, SG614111030000000030001] 8 [SG614111010000000010001, SG614111040000000040001, SG614111030000000030001, SG614111020000000020001] 9 [SG614111020000000020001, SG614111010000000010001, SG614111030000000030001, SG614111040000000040001] 10 [SG614111020000000020001, SG614111010000000010001, SG614111040000000040001, SG614111030000000030001] 11 [SG614111020000000020001, SG614111030000000030001, SG614111010000000010001, SG614111040000000040001] 12 [SG614111020000000020001, SG614111030000000030001, SG614111040000000040001, SG614111010000000010001] 13 [SG614111020000000020001, SG614111040000000040001, SG614111010000000010001, SG614111030000000030001] 14 [SG614111020000000020001, SG614111040000000040001, SG614111030000000030001, SG614111010000000010001] 15 [SG614111030000000030001, SG614111010000000010001, SG614111020000000020001, SG614111040000000040001] 16 [SG614111030000000030001, SG614111010000000010001, SG614111040000000040001, SG614111020000000020001] 17 [SG614111030000000030001, SG614111020000000020001, SG614111010000000010001, SG614111040000000040001] 18 [SG614111030000000030001, SG614111020000000020001, SG614111040000000040001, SG614111010000000010001] 19 [SG614111030000000030001, SG614111040000000040001, SG614111010000000010001, SG614111020000000020001] 20 [SG614111030000000030001, SG614111040000000040001, SG614111020000000020001, SG614111010000000010001] 21 [SG614111040000000040001, SG614111010000000010001, SG614111020000000020001, SG614111030000000030001] 22 [SG614111040000000040001, SG614111010000000010001, SG614111030000000030001, SG614111020000000020001] 23 [SG614111040000000040001, SG614111020000000020001, SG614111010000000010001, SG614111030000000030001] 24 [SG614111040000000040001, SG614111020000000020001, SG614111030000000030001, SG614111010000000010001] 25 [SG614111040000000040001, SG614111030000000030001, SG614111010000000010001, SG614111020000000020001] 26 [SG614111040000000040001, SG614111030000000030001, SG614111020000000020001, SG614111010000000010001] 27 测试组合： 28 C(4, 1) = 4 29 [SG614111010000000010001] 30 [SG614111020000000020001] 31 [SG614111030000000030001] 32 [SG614111040000000040001] 33 C(4, 2) = 6 34 [SG614111010000000010001, SG614111020000000020001] 35 [SG614111010000000010001, SG614111030000000030001] 36 [SG614111010000000010001, SG614111040000000040001] 37 [SG614111020000000020001, SG614111030000000030001] 38 [SG614111020000000020001, SG614111040000000040001] 39 [SG614111030000000030001, SG614111040000000040001] 40 C(4, 3) = 4 41 [SG614111010000000010001, SG614111020000000020001, SG614111030000000030001] 42 [SG614111010000000010001, SG614111020000000020001, SG614111040000000040001] 43 [SG614111010000000010001, SG614111030000000030001, SG614111040000000040001] 44 [SG614111020000000020001, SG614111030000000030001, SG614111040000000040001] 45 C(4, 4) = 1 46 [SG614111010000000010001, SG614111020000000020001, SG614111030000000030001, SG614111040000000040001]