数据结构--二叉树深度优先遍历

public List<Integer> dfs(TreeNode root)
{
	List<Integer> list = new ArrayList<>();
	Stack<TreeNode> stack = new Stack<>();

	if(root == null)
		return list;
	
	stack.push(root);

	while(!stack.isEmpty())
	{
		TreeNode t = stack.pop();
		if(t.right != null)
			stack.push(t.right);
		if(t.left != null)
			stack.push(t.left);
		list.add(t.val);
	}
	return list;
}