http://itfish.net/article/50576.html
计算出来双色球33选6个红球排列组合所有的组合，要求最小化算法时间。
1,23,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33
排列组合后总共有1107568中情况(1107568 = 33!/(33-6)!*6!)
其中算法核心为：最小组合(1,2,3,4,5,6) , 最大组合(28,29,30,31,32,33), 每一组组合规律为 (A<B<C<D<E<F) 。
1.扩展成 排列组合 n个数中取m个的数的组合结果
2.根据用户选的结果统计各个组合的选中数量

import java.util.*;

/**
 * 排列组合
 *
 * @author 咋个办呢
 */
public class PermutationsCombinations {

    /**
     * 递归算法核心
     *
     * @param pce
     * @param w
     * @param m
     */
    private static void calpce(int[] pce, int w, int m) {
        if (pce[w] + 1 > (m - pce.length + w + 1)) {
            if (w > 0) {
                calpce(pce, w - 1, m);
                pce[w] = pce[w - 1] + 1;
            } else {
                pce[w] = pce[w] + 1;
            }
        } else {
            pce[w] = pce[w] + 1;
        }
    }
/**计算从m个数选n个的组合数量  n<=m */
    private static int sumCount(int m, int n) {
        int a = 1, c = 1;
        for (int _m = m; _m > (m - n); _m--) {
            a = a * _m;
        }
        for (int _n = n; _n > 0; _n--) {
            c = c * _n;
        }
        return a / c;
    }

    public static void main(String[] args) {
        List<String> redAllType = redAllType();
        List<String> redBlue = addBlue(redAllType);

        test(redAllType);
    }

    static List<String> redAllType() {
        int all = 33;
        int take = 6;
        int[] pces = new int[all];

        for (int i = 0; i < pces.length; i++) {
            pces[i] = i + 1;
            if (i % 11 == 0) {
                System.out.println();
            }
            System.out.print(pces[i] + ",");
        }

        System.out.println();

        int sumc = sumCount(all, take);

        System.out.println("排列组合后共有" + sumc + "个组合。");

        int[] pce = new int[take];
        for (int i = 0; i < take; i++) {
            pce[i] = i + 1;

        }
        int count = 0;
        long t1 = System.currentTimeMillis();
        ArrayList<String> redAllType = new ArrayList<>(sumc);
        while (count < sumc) {
            count++;
//          System.out.println(String.format("[%d,%d,%d,%d,%d,%d]",pce[0],pce[1],pce[2],pce[3],pce[4],pce[5]));
//            System.out.println(Arrays.toString(pce));
            redAllType.add(Arrays.toString(pce));
            calpce(pce, take - 1, all);
        }
        long t2 = System.currentTimeMillis();

        System.out.println("耗时:" + (t2 - t1) + "ms,计数总数:" + (count));
        return redAllType;
    }

    static List<String> addBlue(List<String> redAllType) {
        long t1 = System.currentTimeMillis();
        ArrayList<String> all = new ArrayList<>();
        int size = redAllType.size();
        for (int i = 1; i <= 16; i++) {
            for (int j = 0; j < size; j++) {
                all.add(redAllType.get(j).replace("]", "," + i + "]"));
            }
        }
        long t2 = System.currentTimeMillis();
        System.out.println("添加篮球 耗时:" + (t2 - t1) + "ms,计数总数:" + (all.size())); //17721088
//        System.out.println(all.toString());
        return all;
    }


    static void test(List<String> all) {
        int count = 10000 * 1000;// 假设有count 个人随机选了号码
        HashMap<String, KeyCount> allMap = new HashMap<>();
        int allCount = all.size();
        for (int i = 0; i < allCount; i++) {
            allMap.put(all.get(i), new KeyCount(all.get(i)));
        }

        //模拟选中的号码
        List<String> hasType = new ArrayList<>(count);
        Random random = new Random();
        for (int i = 0; i < count; i++) {
            hasType.add(all.get(random.nextInt(allCount)));
        }
        long t1 = System.currentTimeMillis();
        //统计 各种号码的个数
        for (int i = 0; i < count; i++) {
            allMap.get(hasType.get(i)).count++;
        }

        Collection<KeyCount> values = allMap.values();
        ArrayList<KeyCount> list = new ArrayList<>(values);
        Collections.sort(list, new Comparator<KeyCount>() {
            @Override
            public int compare(KeyCount arg0, KeyCount arg1) {
                int count0 = arg0.count;
                int count1 = arg1.count;
                if (count0 > count1) {
                    return 1;
                } else if (count0 == count1) {
                    return 0;
                } else {
                    return -1;
                }
            }
        });

        long t2 = System.currentTimeMillis();
        System.out.println("统计结果 耗时:" + (t2 - t1));

        for (int i = 0; i < allCount; i++) {
                if(list.get(i).count>6){
                    break;
                }

            System.out.println(list.get(i));
        }
    }

    static class KeyCount {
        public String key;
        public int count;

        public KeyCount(String key) {
            this.key = key;
        }

        @Override
        public String toString() {
            return "KeyCount{" +
                    "key='" + key + '\'' +
                    ", count=" + count +
                    '}';
        }
    }
}