参数的排列组合2

参数的排列组合2
参数的取值范围是:[“a”,”b”,”c”,”d”],求其所有的排列组合
先给出答案:
共15个,分别是:
abc, d, abd, b, c, a, ac, ad, bcd, ab, bc, acd, abcd, bd, cd

单元测试:

    @Test
    public void test_factorialaa(){
        String base[]=new String[]{"a","b","c","d"};
        Set<String>result=AssembleUtil.assemble( base, 0, base.length,true);
        System.out.println(result.size());
        System.out.println(result);
    }

核心代码:

package com.common.util;

import com.string.widget.util.ValueWidget;

import java.util.HashSet;
import java.util.Set;

/** * Created by huangweii on 2016/1/23. */
public class AssembleUtil {
    /*** * * @param base :[a,b,c,d] * @param times * @param remaining : 剩余要选择的个数 * @return */
    public static void assemble(Set<String> result, StringBuffer buffer, String base[], int times, int remaining, boolean isSort){
        if(remaining<=1){
            buffer.append(base[base.length-1]);
            addElementBySort(result, buffer, isSort);
        }else{
            for(int i=0;i<remaining;i++){
                StringBuffer bufferTmp=new StringBuffer(buffer);
                bufferTmp.append(base[base.length-1-i]);
                addElementBySort(result, bufferTmp, isSort);
                assemble(result,bufferTmp, SystemHWUtil.aheadElement(base,base.length-1-i), times, remaining-1,isSort);
            }
        }

    }

    /*** * * @param base * @param times * @param remaining : 剩余要选择的个数 * @param isSort : 是否对"acb"进行排序,<br />排序结果:"abc" * @return */
    public static Set<String> assemble( String base[], int times, int remaining, boolean isSort){
        Set<String>result=new HashSet<String>();
        StringBuffer buffer=new StringBuffer();
        AssembleUtil.assemble(result,new StringBuffer(), base, 0, base.length,true);
        return result;
    }
    public static void addElementBySort(Set<String> result, StringBuffer buffer, boolean isSort) {
        String str=buffer.toString();
        if(isSort){
            str= ValueWidget. sortStr(str);
        }
        result.add(str);
    }
    /*** * 参数的取值个数,ab和ba算一种 * @param argCount * @return */
    public static int getAssembleSum(int argCount){
        int sum=0;
        for(int i=0;i<argCount;i++){
            int count=i+1;//参数组合的个数
            sum+=(SystemHWUtil. factorial(argCount,count)/SystemHWUtil.arrayArrange(count));
        }
        return sum;
    }

}