From 81a23a1f9307ce42bfa215c9d60356d7d25df76d Mon Sep 17 00:00:00 2001
From: Liam Huang <liamhuang0205@gmail.com>
Date: Wed, 10 Oct 2018 23:46:15 +0800
Subject: [PATCH] [09_queue] linked_queue, done.

---
 c-cpp/09_queue/linked_queue.hpp | 75 +++++++++++++++++++++++++++++++++
 1 file changed, 75 insertions(+)
 create mode 100644 c-cpp/09_queue/linked_queue.hpp

diff --git a/c-cpp/09_queue/linked_queue.hpp b/c-cpp/09_queue/linked_queue.hpp
new file mode 100644
index 0000000..1372775
--- /dev/null
+++ b/c-cpp/09_queue/linked_queue.hpp
@@ -0,0 +1,75 @@
+/**
+ * Created by Liam Huang (Liam0205) on 2018/10/10.
+ */
+
+#ifndef QUEUE_LINKED_QUEUE_HPP_
+#define QUEUE_LINKED_QUEUE_HPP_
+
+#include <memory>
+
+template <typename T>
+struct Node {
+    using ptr_t = std::shared_ptr<Node<T>>;
+    T     data;
+    ptr_t next;
+
+    Node(T data_) : data(data_), next(nullptr) {}
+    Node() : next(nullptr) {}
+};
+
+template <typename T>
+class LinkedQueue {
+  public:
+    using node_type  = Node<T>;
+    using node_ptr_t = typename node_type::ptr_t;
+
+  private:
+    node_ptr_t head_        = nullptr;
+    node_ptr_t before_tail_ = nullptr;
+
+  public:
+    LinkedQueue()  = default;
+    ~LinkedQueue() = default;
+    LinkedQueue(const LinkedQueue& other) = default;
+    LinkedQueue& operator=(const LinkedQueue& rhs) = default;
+    LinkedQueue(LinkedQueue&& other) = default;
+    LinkedQueue& operator=(LinkedQueue&& rhs) = default;
+
+  public:
+    void enqueue(T item) {
+        if (nullptr == head_) {
+            head_ = std::make_shared<node_type>(item);
+            before_tail_ = head_;
+        } else {
+            before_tail_->next = std::make_shared<node_type>(item);
+            before_tail_ = before_tail_->next;
+        }
+    }
+    T head() const {
+        if (nullptr != head_) {
+            return head_->data;
+        } else {
+            throw "Fetch data from an empty queue!";
+        }
+    }
+    void dequeue() {
+        if (nullptr != head_) {
+            head_ = head_->next;
+            if (nullptr == head_) {
+                before_tail_ = nullptr;
+            }
+        } else {
+            throw "Pop data from an empty queue!";
+        }
+    }
+
+  public:
+    template <typename UnaryFunc>
+    void traverse(UnaryFunc do_traverse) {
+        for (node_ptr_t work = head_; nullptr != work; work = work->next) {
+            do_traverse(work->data);
+        }
+    }
+};
+
+#endif  // QUEUE_LINKED_QUEUE_HPP_