字符串所有可能的排列 例如abcd等等 递归算法和排列组合知识结合

可以用在md5编码等

package test;import java.util.ArrayList;import java.util.Collections;import java.util.List;import com.eetrust.raf.core.utils.encrypt.SecureMD5;/** *  * @author chenhui *  */public class Test2 {private StringBuilder builder = null;private static String KEY = "abcdef";private static String DBPWD = "AzoAMg9rWj";/** * @param str *            字符串str中每个字符都不相同 * @return 字符串str所有可能的排列 */public List<String> doCompute(String str) {List<String> list = new ArrayList<String>();List<String> temp = null;if (str.length() == 1) {list.add(str);return list;} else {char ch = str.charAt(0);temp = doCompute(str.substring(1));for (int j = 0; j < temp.size(); j++) {String s = temp.get(j);builder = new StringBuilder(s.length() + 1);// 将ch分别放到s.length() + 1个位置for (int k = 0; k < s.length() + 1; k++) {builder.append(s.substring(0, k));builder.append(ch);builder.append(s.substring(k, s.length()));list.add(j, builder.toString());builder.delete(0, s.length() + 1);}}for (int i = 0; i < temp.size(); i++) {temp.remove(i);}temp = null;return list;}}private static boolean vString(String str){//System.out.println("验证过：" + str);return SecureMD5.passDecrypt(DBPWD,KEY).equals(str);}/** * @param args */public static void main(String[] args) {// TODO Auto-generated method stubTest2 abc = new Test2();long t1 = System.currentTimeMillis();List<String> list = abc.doCompute("89123");long t2 = System.currentTimeMillis();Collections.sort(list);long t3 = System.currentTimeMillis();for (String s : list) {if (vString(s)) {System.out.println("::" + s);return;}}System.out.println(t2 - t1);System.out.println(t3 - t2);}}