fix compare error

priority_queue/src/priority_queue.hpp

@@ -82,7 +82,12 @@ class priority_queue {
    */
   void push(const T &e) {
     Node *new_node = new Node(e);
-    root = SkewMerge(root, new_node);
+    try {
+      root = SkewMerge(root, new_node);
+    } catch (...) {
+      delete new_node;
+      throw;
+    }
     ++node_count;
   }
   /**
@@ -111,6 +116,7 @@ class priority_queue {
    * clear the other priority_queue.
    */
   void merge(priority_queue &other) {
+    if (other.root == root) return;
     root = SkewMerge(root, other.root);
     node_count += other.node_count;
     other.root = nullptr;