Add destructors to the C++ codes.

codes/cpp/chapter_stack_and_queue/array_queue.cpp

@@ -21,6 +21,10 @@ public:
         nums = new int[capacity];
     }
 
+    ~ArrayQueue() {
+        delete[] nums;
+    }
+
     /* 获取队列的容量 */
     int capacity() {
         return cap;
@@ -117,5 +121,8 @@ int main() {
         PrintUtil::printVector(queue->toVector());
     }
 
+    // 释放内存
+    delete queue;
+
     return 0;
 }