需求

之前做过堆栈，优化递归实现树形结构，最近遇到一个新的需求，将树形结构转化为列表，很多情况下都是使用递归来处理，因为该方式逻辑简单，其实一般情况下如果不牵扯单io操作，多层递归也不会有什么问题，想了一下这块也可以用堆栈做一个优化，闲来无事于是实现了一下。

代码实现

Dict类

static class Dict {
		public String code;
		public String name;
		public String parentCode;
		public List<Dict> children;
		public Dict(String code, String name, String parentCode) {
			this(code, name, parentCode, new ArrayList<>());
		}
		public Dict(String code, String name,String parentCode, List<Dict> children) {
			this.code = code;
			this.name = name;
			this.children = children;
			this.parentCode = parentCode;
		}
		
		public Dict(Dict dict) {
			this(dict.code, dict.name, dict.parentCode);
		}
		
	}

造数据方法

List<Dict> fakeDictData() {
		List<Dict> dict = new ArrayList<>();
		dict.add(new Dict("001", "编码-001", ""));
		dict.add(new Dict("002", "编码-002", "",Arrays.asList(new Dict("0021", "编码-0021", "002"),
				new Dict("0022", "编码-0022", "", Arrays.asList(new Dict("00221", "编码-00221", "0022"), new Dict("00222", "编码-00222", "0022"))))));
		System.out.println(JSON.toJSONString(dict));
		return dict;
	}

递归

/**
	 * 树形转列表-递归
	 */
	@Test
	public void testTree2ListRecuruly() {
		
		List<Dict> dict = fakeDictData();
		
		Stack<Dict> stack = new Stack<>();
		
		dict.forEach(d -> stack.push(d));
		
		List<Dict> newDict = new ArrayList<>();
		
		tree2ListRecuruly(dict, newDict);
		
		newDict.sort((d1,d2) -> d1.code.compareTo(d2.code));
		
		System.out.println(JSON.toJSONString(newDict));
		
	}
	
	
	public void tree2ListRecuruly(List<Dict> dictTree, List<Dict> dictList) {
		for(Dict d : dictTree) {
			dictList.add(new Dict(d));
			if(!d.children.isEmpty()) {
				tree2ListRecuruly(d.children, dictList);
			}
		}
	}

堆栈

/**
	 * 树形转列表-2
	 */
	@Test
	public void tree2List2() {
		List<Dict> dict = fakeDictData();
		
		Stack<List<Dict>> stack = new Stack<>();
		
		stack.push(dict);
		
		List<Dict> newDict = new ArrayList<>();
		while(!stack.isEmpty()) {
			List<Dict> pop = stack.pop();
			for(Dict d : pop) {
				newDict.add(new Dict(d));
				if(!d.children.isEmpty()) {
					stack.push(d.children);
				}
			}
		}
		
		newDict.sort((d1,d2) -> d1.code.compareTo(d2.code));
		
		System.out.println(JSON.toJSONString(newDict));
		
	}

比较了一下，输出结果和递归的保持一致，优化完成！