java实现递归算法两种方式

男娘i 2024-04-08 11:21 63阅读 0赞

@Override
    public List<CategoryEntity> listWithTree() {
        //1,查出所有分类
        List<CategoryEntity> entities = baseMapper.selectList(null);
        //2,组装成父子树形结构
        //2.1 找到所有的一级分类
        List<CategoryEntity> level1Menus = entities.stream().filter(categoryEntity ->
             categoryEntity.getParentCid() == 0
        ).map((menu)->{
            menu.setChildren(getChildrens(menu,entities));
            return menu;
        }).sorted((menu1,menu2)->{
            return (menu1.getSort() == null?0:menu1.getSort()) - (menu2.getSort()==null?0:menu2.getSort());
        }).collect(Collectors.toList());
        return level1Menus;
    }
    //递归查找所有菜单的子菜单
    private List<CategoryEntity> getChildrens(CategoryEntity root,List<CategoryEntity> all){
        List<CategoryEntity> chirdren = all.stream().filter(categoryEntity -> {
                return categoryEntity.getParentCid() == root.getCatId();
        }).map(categoryEntity -> {
            //找到子菜单
            categoryEntity.setChildren(getChildrens(categoryEntity,all));
            return categoryEntity;
        }).sorted((menu1,menu2)->{
            //菜单的排序
            return (menu1.getSort() == null?0:menu1.getSort()) - (menu2.getSort()==null?0:menu2.getSort());
        }).collect(Collectors.toList());
        return chirdren;
    }

递归算法二

private List<Map<String, Object>> getMenu(List<MenuCopy1> menuCopy1s , Integer pid){
            List<Map<String, Object>> mapList = new ArrayList<>();
            for (int i = 0; i < menuCopy1s.size(); i++) {
                Map<String,Object> map = null;
                MenuCopy1 menuCopy1 = menuCopy1s.get(i);
                if (pid == menuCopy1.getPid()){
                    map = new HashMap<>();
                    map.put("id",menuCopy1.getId());
                    map.put("text",menuCopy1.getText());
                    map.put("url",menuCopy1.getUrl());
                    map.put("nodes",getMenu(menuCopy1s,menuCopy1.getId()));
                }
                if (map!=null){
                    List<Map<String, Object>> nodes = (List<Map<String, Object>>) map.get("nodes");
                    if (nodes.size()<=0){
                        map.remove("nodes");
                    }
                    mapList.add(map);
                }
            }
            return mapList;
        }