遞歸實現：java多組List所有的排列組合

	private static <T> List<List<T>> getDescartes(List<List<T>> list) {
        List<List<T>> returnList = new ArrayList<>();
        descartesRecursive(list, 0, returnList, new ArrayList<T>());
        return returnList;
    }

    /**
     * 遞歸實現
     * 原理：從原始list的0開始依次遍歷到最後
     *
     * @param originalList 原始list
     * @param position     當前遞歸在原始list的position
     * @param returnList   返回結果
     * @param cacheList    臨時保存的list
     */
    private static <T> void descartesRecursive(List<List<T>> originalList, int position, List<List<T>> returnList, List<T> cacheList) {
        List<T> originalItemList = originalList.get(position);
        for (int i = 0; i < originalItemList.size(); i++) {
            //最後一個複用cacheList，節省內存
            List<T> childCacheList = (i == originalItemList.size() - 1) ? cacheList : new ArrayList<>(cacheList);
            childCacheList.add(originalItemList.get(i));
            if (position == originalList.size() - 1) {//遍歷到最後退出遞歸
                returnList.add(childCacheList);
                continue;
            }
            descartesRecursive(originalList, position + 1, returnList, childCacheList);
        }
    }