任意價格相加在某個範圍內

package com.louisgeek.price;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;

public class CaseTestPrice {

    /**
     * 用遞迴的思想來求排列跟組合  然後應用到滿減活動
     */
    public static void main(String[] args) {

        // 一堆書的價格
 

        Object[] tmp = { 44.2, 56.8, 77.6, 88.9, 100.8, 110.6 };
        // Object[] tmp = str.split(" ");
        int minCount = 200;// 滿200
        int maxCount = 220;// 自己認為的最大限制
        int num = 0;
        ArrayList<Object[]> rs = RandomC(tmp);
        // ArrayList<Object[]> rs = cmn(tmp, 3);//3個的組合
        // ArrayList<Object[]> rs = cmn(tmp, 4);//4個的組合
 

        for (int i = 0; i < rs.size(); i++)

        {
            // System.out.print(i+"=");
            Double countTemp = 0.0;
            String strTemp = "";
            for (int j = 0; j < rs.get(i).length; j++) {
                countTemp = countTemp + Double.parseDouble(rs.get(i)[j].toString());
                // System.out.print(rs.get(i)[j] + ",");
 

                strTemp += rs.get(i)[j] + ",";
            }
            // System.out.println();
            if (minCount < countTemp && countTemp <= maxCount) {
                num++;
                System.out.println("滿" + minCount + "減，方案" + num + ":" + countTemp + "\n組合是：" + strTemp + "\n");
            }

        }

    }

    // 求一個數組的任意組合
    static ArrayList<Object[]> RandomC(Object[] source) {
        ArrayList<Object[]> result = new ArrayList<Object[]>();
        if (source.length == 1) {
            result.add(source);
        } else {
            Object[] psource = new Object[source.length - 1];
            for (int i = 0; i < psource.length; i++) {
                psource[i] = source[i];
            }
            result = RandomC(psource);
            int len = result.size();// fn組合的長度
            result.add((new Object[] { source[source.length - 1] }));
            for (int i = 0; i < len; i++) {
                Object[] tmp = new Object[result.get(i).length + 1];
                for (int j = 0; j < tmp.length - 1; j++) {
                    tmp[j] = result.get(i)[j];
                }
                tmp[tmp.length - 1] = source[source.length - 1];
                result.add(tmp);
            }

        }
        return result;
    }

    // 求指定長度的陣列任意組合
    static ArrayList<Object[]> cmn(Object[] source, int n) {
        ArrayList<Object[]> result = new ArrayList<Object[]>();
        if (n == 1) {
            for (int i = 0; i < source.length; i++) {
                result.add(new Object[] { source[i] });

            }
        } else if (source.length == n) {
            result.add(source);
        } else {
            Object[] psource = new Object[source.length - 1];
            for (int i = 0; i < psource.length; i++) {
                psource[i] = source[i];
            }
            result = cmn(psource, n);
            ArrayList<Object[]> tmp = cmn(psource, n - 1);
            for (int i = 0; i < tmp.size(); i++) {
                Object[] rs = new Object[n];
                for (int j = 0; j < n - 1; j++) {
                    rs[j] = tmp.get(i)[j];
                }
                rs[n - 1] = source[source.length - 1];
                result.add(rs);
            }
        }
        return result;
    }

}

輸出：

滿200減，方案1:210.7
組合是：44.2,77.6,88.9,

滿200減，方案2:201.8
組合是：44.2,56.8,100.8,

滿200減，方案3:211.6
組合是：44.2,56.8,110.6,

滿200減，方案4:211.39999999999998
組合是：100.8,110.6,