1.递归法public class Solution { Listint result new Listint(); public IListint InorderTraversal(TreeNode root) { if (root null) return result; InorderTraversal(root.left); result.Add(root.val); InorderTraversal(root.right); return result; } }2.迭代法public class Solution { StackTreeNode stack new StackTreeNode(); Listint result new Listint(); public IListint InorderTraversal(TreeNode root) { TreeNode current root; while (current ! null || stack.Count 0) { while (current ! null) { stack.Push(current); current current.left; } current stack.Pop(); result.Add(current.val); current current.right; } return result; } }