Implement nextTreeData()

bintree.c

@@ -68,6 +68,27 @@ TreeNode *addToTree(TreeNode *root, const void *data, size_t dataSize, CompareFc
 // push the top node and push all its left nodes.
 void *nextTreeData(TreeNode *root)
 {
+    static StackNode *stack = NULL;
+    static TreeNode *current = NULL;
+
+    if(root != NULL){
+        clearStack(stack);
+        stack = NULL;
+        current = root;
+    }
+
+    while (current != NULL)
+    {
+        stack = push(stack, current);
+        current = current->left;
+    }
+
+    TreeNode *node = (TreeNode *)top(stack);
+    stack = pop(stack);
+
+    current = node->right;
+
+    return node->data;
     
 }