From 2d4d030a8620f20169cb41e2c10081a822b99885 Mon Sep 17 00:00:00 2001
From: Alex-Usmanov <40719830+Alex-Usmanov@users.noreply.github.com>
Date: Fri, 19 Oct 2018 19:58:10 +0500
Subject: [PATCH 1/2] Implemented linked list data structure

---
 Data Structures/linkedList.py | 145 ++++++++++++++++++++++++++++++++++
 1 file changed, 145 insertions(+)
 create mode 100644 Data Structures/linkedList.py

diff --git a/Data Structures/linkedList.py b/Data Structures/linkedList.py
new file mode 100644
index 0000000..f538776
--- /dev/null
+++ b/Data Structures/linkedList.py	
@@ -0,0 +1,145 @@
+class Node:
+    value = 0
+    next_ = 0
+
+    def __init__(self, value=None, next_=None):
+        self.value = value
+        self.next_ = next_
+
+
+class linkedList:
+    __head = Node()
+    __tail = Node()
+    __nodes = 0
+
+    @property
+    def head(self):
+        """
+        Returns the head node (first) of the linked list
+        """
+        return self.__head
+
+    @property
+    def tail(self):
+        """
+        Returns the tail node (last) of the linked list
+        """
+        return self.__tail
+
+    @property
+    def nodes(self):
+        """
+        Returns the number of nodes of the linked list
+        """
+        return self.__nodes
+
+    def getNode(self, index: int):
+        """
+        Returns the node by the given index
+        """
+        currentNode = self.__head
+
+        for i in range(index):
+            if currentNode.next_ == None:
+                print("Node by the current index doesn't exists! Returning None")
+                return None
+            else:
+                currentNode = currentNode.next_
+
+        return currentNode
+
+    def getValue(self, index: int):
+        """
+        Returns the value of the node by the given index
+        """
+        currentNode = self.__head
+
+        for i in range(index):
+            currentNode = currentNode.next_
+
+        try:
+            return currentNode.value
+
+        except AttributeError:
+            print("Node by the current index doesn't exists")
+
+    def append(self, value):
+        """
+        Inserts a node with the given value to the end of the linked list
+        """
+        toAppend = Node(value)
+        if self.__nodes == 0:
+            self.__head = toAppend
+            self.__tail = toAppend
+            self.__head.next_ = self.__tail
+        else:
+            self.__tail.next_ = toAppend
+            self.__tail = toAppend
+
+        self.__nodes += 1
+
+    def shift(self, value):
+        """
+        Inserts a node with the given value to the beginning of the linked list
+        """
+        node = Node(value)
+        if self.__nodes == 0:
+            self.__head = node
+            self.__tail = node
+            self.__head.next_ = self.__tail
+        else:
+            head = self.__head
+            node.next_ = head
+            self.__head = node
+        self.__nodes += 1
+
+    def insert(self, index: int, value):
+        """
+        Inserts the value AFTER index given in the function
+        """
+        nodeToInsert = Node(value)
+        if self.__nodes == 0:
+            self.__head = nodeToInsert
+            self.__tail = nodeToInsert
+            self.__head.next_ = self.__tail
+
+        else:
+            try:
+                node = self.getNode(index)
+                nodeToInsert = Node(value, node.next_.next_)
+                node.next_ = nodeToInsert
+            except AttributeError:
+                print("Couldn't insert! Given index is too big!")
+
+        self.__nodes += 1
+
+    def pop(self, index=0):
+        """
+        Removes a node by the given index. If not specified - removes the head node
+        """
+        if self.nodes == 2:
+            self.__head = self.__tail
+        if self.nodes == 1:
+            self.__head = Node(None)
+            self.__tail= Node(None)
+        if index == 0:
+            if self.__head.next_ == self.head:
+                self.__head = Node(0)
+            else:
+                self.__head = self.__head.next_
+        else:
+            previousNode = self.getNode(index-1)
+            try:
+                previousNode.next_ = previousNode.next_.next_
+            except AttributeError:
+                print("Node by given index doesn't exists")
+
+        self.__nodes -= 1
+
+    def replace(self, index: int, value):
+        """
+        Changes node's value by the given index to the given value
+        """
+        if index > self.__nodes - 1:
+            node = self.getNode(index)
+            node.value = value

From 50555d2e334c56694973b2cfb390ac422eaa5b11 Mon Sep 17 00:00:00 2001
From: Alex-Usmanov <40719830+Alex-Usmanov@users.noreply.github.com>
Date: Fri, 19 Oct 2018 20:00:39 +0500
Subject: [PATCH 2/2] Implemented queue

Uses linked list class
---
 Data Structures/queue.py | 48 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)
 create mode 100644 Data Structures/queue.py

diff --git a/Data Structures/queue.py b/Data Structures/queue.py
new file mode 100644
index 0000000..fa81a4c
--- /dev/null
+++ b/Data Structures/queue.py	
@@ -0,0 +1,48 @@
+from linkedList import linkedList
+
+
+class queue:
+    __start = 0
+    __end = 0
+    __linkedList = 0
+    __size = 0
+
+    def __init__(self):
+        self.__linkedList = linkedList()
+
+    @property
+    def size(self):
+        return self.__size
+
+    def queue(self, toQueue):
+        """
+        Queues a given element
+        """
+        self.__linkedList.shift(toQueue)
+        self.__size += 1
+
+    def dequeue(self):
+        """
+        Removes the last element from the queue
+        """
+        nodes = self.__linkedList.nodes
+        self.__linkedList.pop(nodes - 1)
+        self.__size -= 1
+
+    def front(self):
+        """
+        Returns the most recently added element
+        """
+        try:
+            return self.__linkedList.head.value
+        except AttributeError:
+            print("The queue is empty")
+    
+    def back(self):
+        """
+        Returns the oldest element
+        """
+        try:
+            return self.__linkedList.head.value
+        except AttributeError:
+            print("The queue is empty")