（原创）java 输出排列组合，’4‘ 不能在第三位，‘3’，‘5’不能相连。

 1 package karl.test;
 2 
 3 import java.util.Iterator;
 4 import java.util.Set;
 5 import java.util.TreeSet;
 6 
 7 public class Test {
 8     private static Set<String> set = new TreeSet<String>();
 9 
10     public static String sort(String prex, String str) {
11         boolean flag = true;
12         int len = str.length();
13         if (str.length() == 1) {
14             set.add(prex + str);
15             flag = false;
16             return prex + str;
17         }
18 
19         for (int i = 0; i < len; i++) {
20             String reststr = str.substring(0, i) + str.substring(i + 1, len);
21             prex += str.charAt(i);
22             sort(prex, reststr);
23             if (flag) {
24                 prex = prex.substring(0, prex.length() - 1);
25                 flag = true;
26             }
27         }
28         return null;
29     }
30 
31     public static void main(String[] args) {
32         String str = "122345";
33         sort("", str);
34         Iterator<String> it = set.iterator();
35         while (it.hasNext()) {
36             String next = it.next();
37             if (next.contains("35") || next.contains("53")
38                     || (next.charAt(3) == '4')) {
49 
40             } else {
41                 System.out.println(next);
42             }
43         }
44     }
45 }