中序遍历用栈实现了一下，虽然判断条件有点多。以后再考虑优化

CMakelists.txt

@@ -1,6 +1,6 @@
 
 # 0. cmake 最低版本号要求
-cmake_minimum_required(VERSION 3.27)
+cmake_minimum_required(VERSION 3.29)
 
 # 0. 项目信息
 project(demo)

mk.bat

@@ -1,8 +1,8 @@
 @REM D:\Lang\cmake-3.27.5-windows-x86_64\bin\cmake.EXE --no-warn-unused-cli -DCMAKE_BUILD_TYPE:STRING=Debug -DCMAKE_EXPORT_COMPILE_COMMANDS:BOOL=TRUE -DCMAKE_C_COMPILER:FILEPATH=D:\Software\mingw64\bin\gcc.exe -DCMAKE_CXX_COMPILER:FILEPATH=D:\Software\mingw64\bin\g++.exe -SF:/OpenDemo/1_vsc_cmake -Bf:/OpenDemo/1_vsc_cmake/build -G "MinGW Makefiles"
 @REM cmake -Bbuild -G "Visual Studio 17 2022"
 
-cmake -B build -G "MinGW Makefiles"
+@REM cmake -B build -G "MinGW Makefiles"
-@REM cmake -B build -G "Unix Makefiles"
+cmake -B build -G "Unix Makefiles"
 
 make -C build
 make -C build install 

src/tree.c

@@ -10,6 +10,7 @@
  */
 #include "tree.h"
 #include "queue.h"
+#include "stack.h"
 
 #if RAVLTREE == 1
 // function declare
@@ -1981,6 +1982,7 @@ void tree_avl_preorder(struct _tree* self, struct _tree_node* root)
 
 void tree_avl_inorder(struct _tree* self, struct _tree_node* root)
 {
+#if 0
     assert(self != NULL);
     if(root == NULL)
     {
@@ -1996,7 +1998,7 @@ void tree_avl_inorder(struct _tree* self, struct _tree_node* root)
         self->print_obj(root->obj);
         if(root->right != NULL)
         {
-            tree_avl_inorder(self, root->right);
+            tree_avl_inorder(self, root->right);  
         }
     }
     else
@@ -2011,6 +2013,56 @@ void tree_avl_inorder(struct _tree* self, struct _tree_node* root)
             tree_avl_inorder(self, root->left);
         }
     }
+#else
+    assert(self != NULL);
+    if(root == NULL)
+    {
+        return;
+    }
+
+    struct _tree_node *node = root;
+
+    stack_t stack = stack_new();
+    stack_init(stack, sizeof(struct _tree_node*));
+
+    if(!self->_right_priority)
+    {
+        while(node != NULL || !stack->empty(stack))
+        {
+            while(node != NULL)
+            {
+                stack->push(stack, &node);
+                node = node->left;
+            }
+
+            do
+            {
+                stack->pop(stack, &node);
+                self->print_obj(node->obj);
+            }while(node->right == NULL && !stack->empty(stack));
+            node = node->right;
+        }
+    }
+    else
+    {
+        while(node != NULL || !stack->empty(stack))
+        {
+            while(node != NULL)
+            {
+                stack->push(stack, &node);
+                node = node->right;
+            }
+
+            do
+            {
+                stack->pop(stack, &node);
+                self->print_obj(node->obj);
+            }while(node->left == NULL && !stack->empty(stack));
+            node = node->left;
+        }
+    }
+    stack_free(stack);
+#endif
 }
 
 void tree_avl_postorder(struct _tree* self, struct _tree_node* root)