From 1c6b5e932ff487f7cd26a1c1bdd7185d44b5f403 Mon Sep 17 00:00:00 2001
From: Wenru Dong <dongwenru.aaron.shenyang@gmail.com>
Date: Thu, 11 Oct 2018 20:03:29 +0100
Subject: [PATCH] implementation of DynamicArray and queue based upon linked
 list in python

---
 python/09_queue/dynamic_array_queue.py | 51 ++++++++++++++++++++++
 python/09_queue/linked_queue.py        | 58 ++++++++++++++++++++++++++
 2 files changed, 109 insertions(+)
 create mode 100644 python/09_queue/dynamic_array_queue.py
 create mode 100644 python/09_queue/linked_queue.py

diff --git a/python/09_queue/dynamic_array_queue.py b/python/09_queue/dynamic_array_queue.py
new file mode 100644
index 00000000..b4228403
--- /dev/null
+++ b/python/09_queue/dynamic_array_queue.py
@@ -0,0 +1,51 @@
+"""
+    Author: Wenru
+"""
+
+from typing import Optional
+
+class DynamicArrayQueue:
+
+    def __init__(self, capacity: int):
+        self._items = []
+        self._capacity = capacity
+        self._head = 0
+        self._tail = 0
+    
+    def enqueue(self, item: str) -> bool:
+        if self._tail == self._capacity:
+            if self._head == 0: return False
+            
+            self._items[0 : self._tail - self._head] = self._items[self._head : self._tail]
+            self._tail -= self._head
+            self._head = 0
+        
+        if self._tail == len(self._items):
+            self._items.append(item)
+        else:
+            self._items[self._tail] = item
+        self._tail += 1
+        return True
+
+    def dequeue(self) -> Optional[str]:
+        if self._head != self._tail:
+            item = self._items[self._head]
+            self._head += 1
+            return item
+    
+    def __repr__(self) -> str:
+        return " ".join(item for item in self._items[self._head:self._tail])
+
+if __name__ == "__main__":
+    q = DynamicArrayQueue(10)
+    for i in range(10):
+        q.enqueue(str(i))
+    print(q)
+
+    for _ in range(3):
+        q.dequeue()
+    print(q)
+
+    q.enqueue("7")
+    q.enqueue("8")
+    print(q)
\ No newline at end of file
diff --git a/python/09_queue/linked_queue.py b/python/09_queue/linked_queue.py
new file mode 100644
index 00000000..4ee4ecf0
--- /dev/null
+++ b/python/09_queue/linked_queue.py
@@ -0,0 +1,58 @@
+"""
+    Queue based upon linked list
+
+    Author: Wenru
+"""
+
+from typing import Optional
+
+class Node:
+    
+    def __init__(self, data: str, next=None):
+        self.data = data
+        self._next = next
+
+class LinkedQueue:
+
+    def __init__(self):
+        self._head: Optional[Node] = None
+        self._tail: Optional[Node] = None
+    
+    def enqueue(self, value: str):
+        new_node = Node(value)
+        if self._tail:
+            self._tail._next = new_node
+        else:
+            self._head = new_node
+        self._tail = new_node
+    
+    def dequeue(self) -> Optional[str]:
+        if self._head:
+            value = self._head.data
+            self._head = self._head._next
+            if not self._head:
+                self._tail = None
+            return value
+    
+    def __repr__(self) -> str:
+        values = []
+        current = self._head
+        while current:
+            values.append(current.data)
+            current = current._next
+        return "->".join(value for value in values)
+
+
+if __name__ == "__main__":
+    q = LinkedQueue()
+    for i in range(10):
+        q.enqueue(str(i))
+    print(q)
+
+    for _ in range(3):
+        q.dequeue()
+    print(q)
+
+    q.enqueue("7")
+    q.enqueue("8")
+    print(q)