Java练习题-输入一个字符串，输出该字符串中字符的所有组合

import java.util.Collections;
import java.util.Comparator;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.List;
import java.util.Set;

/**
* 输入一个字符串，输出该字符串中字符的所有组合。举个例子，如果输入abc，它的组合有a、b、c、ab、ac、bc、abc,组合中不能出现重复的字符。
*
* @author Tang
*
*/
public class Test {

public static void main(String[] args) {
    List list = getResultList("12345");
    System.out.println(list);
}

public static List getResultList(String s) {
    HashSet set = new HashSet();
    traverseCharArray(s.toCharArray(), set);
    List list = new LinkedList(set);
    Collections.sort(list, new Comparator() {
        public int compare(String o1, String o2) {
            if (o1.length() == o2.length()) {
                return o1.compareToIgnoreCase(o2);
            } else {
                return o1.length() - o2.length();
            }
        }
    });
    return list;
}

public static void traverseCharArray(char[] chars, HashSet set) {
    for (int i = 0; i < chars.length; i++) {
        recursionMerge(chars[i], getOther(chars, i), set);
    }
}

public static Set recursionMerge(char c, char[] chars, HashSet set) {
    Set merges = new HashSet();
    String merge = merge(c + "", new String(chars));
    merges.add(merge);
    set.add(merge);

    for (int i = 0; i < chars.length; i++) {
        Set mergeSet = recursionMerge(chars[i], getOther(chars, i), set);
        for (String str : mergeSet) {
            String merge2 = merge(c + "", str);
            set.add(merge2);
            merges.add(merge2);
        }
    }
    return merges;
}

public static char[] getOther(char[] c1, int index) {
    StringBuffer buffer = new StringBuffer(new String(c1));
    buffer.deleteCharAt(index);
    return buffer.toString().toCharArray();
}

public static String merge(String s1, String s2) {
    return s1 + s2;
}

}

转载于:https://my.oschina.net/tangzhichao/blog/781452