diff --git a/bintree.c b/bintree.c
index 8687439..298466f 100644
--- a/bintree.c
+++ b/bintree.c
@@ -53,14 +53,45 @@ TreeNode *addToTree(TreeNode* root, const void* data, size_t dataSize, CompareFc
             
 }
 
-// Iterates over the tree given by root. Follows the usage of strtok. If tree is NULL, the next entry of the last tree given is returned in ordering direction.
-// Use your implementation of a stack to organize the iterator. Push the root node and all left nodes first. On returning the next element,
+// Iterates over the tree given by root. Follows the usage of strtok. If tree is NULL,
+// the next entry of the last tree given is returned in ordering direction.
+// Use your implementation of a stack to organize the iterator. Push the root node and
+// all left nodes first. On returning the next element,
 // push the top node and push all its left nodes.
 void *nextTreeData(TreeNode *root)
 {
+    static StackNode *stack = NULL;
+    if (root != NULL) {
+        clearStack(stack);
+        stack = push(NULL, root);
+        while(root->left != NULL) {
+            root = root->left;
+            stack = push(stack,root);
+        }
+    }
+
+    if (stack == NULL) {
+        return NULL;
+    }
+
+    TreeNode* result = (TreeNode*)top(stack);
+    stack = pop(stack);
+    root = result;
+    
+    if (root->right != NULL) {
+        root = root->right;
+        stack = push(stack,root);
+        while(root->left != NULL) {
+            root = root->left;
+            stack = push(stack,root);
+        }
+    }
+    return result->data;
 
 }
 
+
+
 // Releases all memory resources (including data copies).
 void clearTree(TreeNode *root)
 {
diff --git a/stack.c b/stack.c
index 226a36f..0a46615 100644
--- a/stack.c
+++ b/stack.c
@@ -8,7 +8,7 @@
     * `clearStack`: gibt den gesamten Speicher frei. */
 
 // Pushes data as pointer onto the stack.
-StackNode* push(StackNode* stack, void* data) // es gibt bereits ein stack element, dieses wird übergeben + die daten, die in den stack müssen
+StackNode* push(StackNode* stack, void* data)
 {
     //if(!data)
         //return 0; -> nicht notwendig