Free memory after removing

a node from a LinkedList or TreeNode.

codes/cpp/chapter_tree/binary_tree.cpp

@@ -33,6 +33,7 @@ int main() {
     PrintUtil::printTree(n1);
     // 删除结点 P
     n1->left = n2;
+    delete P;  // 释放内存
     cout << endl << "删除结点 P 后\n" << endl;
     PrintUtil::printTree(n1);