diff --git a/bintree.c b/bintree.c
index 5cf82a9..9205425 100644
--- a/bintree.c
+++ b/bintree.c
@@ -12,7 +12,55 @@
 // if isDuplicate is NULL, otherwise ignores duplicates and sets isDuplicate to 1 (or to 0 if a new entry is added).
 TreeNode *addToTree(TreeNode *root, const void *data, size_t dataSize, CompareFctType compareFct, int *isDuplicate)
 {
+    
+    if(root == NULL){
+        //Allocate Memory for Node
+        TreeNode *newNode = calloc(1, sizeof(TreeNode));
+        if(newNode == NULL){
+            return NULL; //Memory allocation failed
+        }
 
+        //Allocate Memory for data
+        newNode->data = malloc(dataSize);
+        if(newNode->data == NULL){
+            free(newNode); //Free unused Memory
+            return NULL;; //Memory allocation failed
+        }
+        newNode->data = data; //Copy Data
+
+        newNode->left = NULL;
+        newNode->right = NULL;
+
+        if(isDuplicate != NULL){
+            *isDuplicate = 0;
+        }
+
+        return newNode;
+
+    }
+    int cmp = compareFct(root->data, data);
+    
+    if(cmp == 0){
+        //Duplicate
+        if(isDuplicate != NULL){
+            //Ignore duplicate
+            *isDuplicate = 1;
+            return root;
+        } else{
+            //Accept duplicate
+            root->right = addToTree(root->right, data, dataSize, compareFct, NULL);
+        }
+    }
+    else if (cmp > 0)
+    {
+        //Data is smaller -> left
+        root->left = addToTree(root->left, data, dataSize, compareFct, isDuplicate);
+    }else{
+        //Data is bigger -> right
+        root->right = addToTree(root->right, data, dataSize, compareFct, isDuplicate);
+    }
+    
+    return root;
 }
 
 // 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.