Edit cours_15.md

slides/cours_15.md

@@ -1131,8 +1131,9 @@ tree_t position(tree_t tree, key_t key) {
                   ? current->right : current->left;
         while (key != current->key && NULL != subtree) {
             current = subtree;
-            subtree = key > current->key ? current->right :
-            current->left;
+            subtree 
+                = key > current->key 
+                      ? current->right : current->left;
         }
     }
     return current;