Added Linked Lists in linear-data-structures

AUTHORS

@@ -1,4 +1,4 @@
 Gagandeep Singh<singh.23@iitj.ac.in>
 Kartikei Mittal<kartikeimittal@gmail.com>
 Umesh<23umesh.here@gmail.com>
-
+Rohan Singh<singh.77@iitj.ac.in>

pydatastructs/linear_data_structures/__init__.py

@@ -2,10 +2,15 @@
 
 from . import (
     arrays,
+    linked_lists
 )
 
 from .arrays import (
     OneDimensionalArray,
     DynamicOneDimensionalArray
 )
+
+from .linked_lists import (
+    DoublyLinkedList
+)
 __all__.extend(arrays.__all__)

pydatastructs/linear_data_structures/linked_lists.py

@@ -0,0 +1,330 @@
+from __future__ import print_function, division
+from pydatastructs.utils.misc_util import _check_type, NoneType
+from pydatastructs.utils import ( 
+    Node
+)
+
+__author__ = 'rohansingh9001'
+
+__all__ = [
+    'DoublyLinkedList',
+    'LinkedList'
+]
+
+class LinkedList(object):
+    '''
+    Abstract class for Linked List in pydatastructs.
+    '''
+    pass
+
+# Class to create a Doubly Linked List 
+class DoublyLinkedList(LinkedList): 
+
+
+    '''
+    A Doubly Linked List Class (abb. DLL)
+
+    Parameters
+    ==========
+
+    None
+
+    Examples
+    ========
+    >>> from pydatastructs import DoublyLinkedLIst as DLL
+    >>> dll = DLL()
+    >>> dll.append(6)
+    >>> arr[0]
+    6
+    >>> dll.head
+    6
+    >>> dll.append(5)
+    >>> dll.appendleft(2)
+    >>> print(dll)
+    [2,6,5]
+    >>> dll[0] = 7.2
+    >>> dll[0]
+    7.2
+    >>> dll.pop(1)
+    6
+    >>> print(dll)
+    [2,5]
+
+    References
+    ==========
+
+    https://www.geeksforgeeks.org/doubly-linked-list/
+
+    '''
+    __slots__ = ['head','tail','length']
+
+    def __init__(self):
+        self.head = NoneType
+        self.tail = NoneType
+        self.length = 0
+
+    def appendleft(self,data):
+        '''
+        appendleft: 
+        takes parameters - data
+            data: type 
+                A valid object type
+                Should be convertible to string using str() method to 
+                use print() method on instance.
+        action - Pushes a new node at the start i.e. left of the DLL.
+        '''
+        self.length += 1
+        newNode = Node(data)
+        if self.head is not NoneType:
+            self.head.prev = newNode
+            newNode.next = self.head
+        self.head = newNode
+
+        if newNode.next == NoneType:
+            self.tail = newNode
+        if newNode.prev == NoneType:
+            self.head = newNode
+
+    def append(self, data):
+        '''
+        append: 
+        takes parameters - data
+            data: type
+                A valid object type.
+                Should be convertible to string using str() method to 
+                use print() method on instance.
+        action - Appends a new node at the end i.e. the right of the DLL.
+        '''
+        self.length += 1
+        newNode = Node(data)
+        if self.tail is not NoneType:
+            self.tail.next = newNode
+            newNode.prev = self.tail
+        self.tail = newNode
+
+        if newNode.next == NoneType:
+            self.tail = newNode
+        if newNode.prev == NoneType:
+            self.head = newNode
+
+    def insertAfter(self, prevNode, data):
+        '''
+        insertAfter:
+        takes parameters - prevNode, data
+            prevNode: Node type 
+                An object of Node class 
+            data: type
+                A valid object type.
+                Should be convertible to string using str() method to
+                use print() method in instance.
+        action - Inserts a new node after the prevNode.
+        '''
+        self.length += 1
+        newNode = Node(data)
+        newNode.next = prevNode.next
+        prevNode.next = newNode
+        newNode.prev = prevNode
+
+        if newNode.next == NoneType:
+            self.tail = newNode
+        if newNode.prev == NoneType:
+            self.head = newNode
+
+    def insertBefore(self, nextNode, data):
+        '''
+        insertBefore:
+        takes parameters - nextNode, data
+            prevNode: Node type
+                An object of Node class
+            data: type
+                A valid object type.
+                Should be convertible to string using str() method to 
+                use print() method in instance.
+        action - Inserts a new node before the newNode.
+        '''
+        self.length += 1
+        newNode = Node(data)
+        newNode.prev = nextNode.prev
+        nextNode.prev = newNode
+        newNode.next = nextNode
+
+        if newNode.next == NoneType:
+            self.tail = newNode
+        if newNode.prev == NoneType:
+            self.head = newNode
+
+    def insertAt(self, index, data):
+        '''
+        insertAt:
+        takes parameters - index, data
+            index: int type
+                An integer i such that 0<= i <= length, where length 
+                refers to the length of the List.
+            data: type
+                A valid object type.
+                Should be convertible to string using str() method to
+                use print() method in instance.
+        action - Inserts a new node at the input index.
+        '''
+        if index > self.length or index < 0 or not (_check_type(index, int)):
+            raise ValueError('Index input out of range/Index is expected to be an Integer.')
+        else:
+            if index == 0:
+                self.appendleft(data)
+            elif index == self.length:
+                self.appendright(data)
+            else:  
+                self.length += 1
+                newNode = Node(data)
+                counter = 0
+                currentNode = self.head
+                while counter != index:
+                    currentNode = currentNode.next
+                    counter += 1
+                currentNode.prev.next = newNode
+                newNode.prev = currentNode.prev
+                currentNode.prev = newNode
+                newNode.next = currentNode
+
+                if newNode.next == NoneType:
+                    self.tail = newNode
+                if newNode.prev == NoneType:
+                    self.head = newNode
+
+    def popleft(self):
+        '''
+        popleft: 
+        takes parameters - None
+        action - Removes the Node from the left i.e. start of the DLL
+         and returns the data from the Node.
+        '''
+        self.length -= 1
+        oldHead = self.head
+        oldHead.next.prev = NoneType
+        self.head = oldHead.next
+        return oldHead.data 
+
+    def popright(self):
+        '''
+        popright:
+        takes parameters - None
+        action - Removes the Node from the right i.e. end of the DLL 
+        and returns the data from the Node.
+        '''
+        self.length -= 1
+        oldTail = self.tail
+        oldTail.prev.next = NoneType
+        self.tail = oldTail.prev
+        return oldTail.data
+
+    def pop(self, index=0):
+        '''
+        pop:
+        takes parameters - index
+            index: int type
+                An integer i such that 0<= i <= length, where length
+                 refers to the length of the List.
+        action - Removes the Node at the index of the DLL and returns
+         the data from the Node.
+        '''
+        if index > self.length or index < 0 or not (_check_type(index, int)):
+            raise ValueError('Index input out of range/Index is expected to be an Integer.') 
+        else:  
+            if index == 0:
+                self.popleft()
+            elif index == self.length:
+                self.popright()
+            else:
+                self.length -= 1
+                counter = 0
+                currentNode = self.head
+                while counter != index:
+                    currentNode = currentNode.next
+                    counter += 1
+                currentNode.prev.next = currentNode.next
+                currentNode.next.prev = currentNode.prev
+                return currentNode.data
+
+    def __getitem__(self, index): 
+        '''
+        __getitem__:
+        takes parameters - index
+            index: int type
+                An integer i such that 0<= i <= length, where length 
+                refers to the length of the List.
+        action - Returns the data of the Node at index.
+        '''
+        if index > self.length or index < 0 or not (_check_type(index, int)):
+            raise ValueError('Index input out of range/Index is expected to be an Integer.')
+        else:     
+            counter = 0
+            currentNode = self.head      
+            while counter != index:
+                currentNode = currentNode.next
+                counter += 1
+            return currentNode.data
+
+    def __setitem__(self, index, data):
+        '''
+        __setitem__:
+        takes parameters - index, data
+            index: int type
+                An integer i such that 0<= i <= length, where length 
+                refers to the length of the List.
+            data: type
+                A valid object type.
+                Should be convertible to string using str() method to use 
+                print() method in instance.
+        action - Sets the data of the Node at the index to the input data.
+        '''
+        if index > self.length or index < 0 or not (_check_type(index, int)):
+            raise ValueError('Index input out of range/Index is expected to be an Integer.')
+        else:  
+            counter = 0
+            currentNode = self.head    
+            while counter != index:
+                currentNode = currentNode.next
+                counter += 1
+            currentNode.data = data
+
+    def __str__(self):
+        '''
+        __str__:
+        takes parameters - None
+        action - Prints the DLL in a list from from the start to the end.
+        '''
+        elements = []
+        currentNode = self.head
+        while currentNode is not NoneType:
+            elements.append(currentNode.data)
+            currentNode = currentNode.next
+        return str(elements)
+
+    def __len__(self):
+        '''
+        __len__:
+        takes parameters - None
+        action - Returns the length of the DLL.
+        '''
+        return self.length
+
+    def isEmpty(self):
+        '''
+        isEmpty:
+        takes parameters - None
+        action - Return a bool value to check if the DLL is empty or not.
+        '''
+        return self.length == 0
+
+if __name__ == '__main__':
+    dll = DoublyLinkedList()
+    dll.append(6)
+    arr[0]
+    dll.head
+    dll.append(5)
+    dll.appendleft(2)
+    print(dll)
+    dll[0] = 7.2
+    dll[0]
+    dll.pop(1)
+    print(dll)

pydatastructs/utils/__init__.py

@@ -2,6 +2,7 @@
 
 from . import misc_util
 from .misc_util import (
-    TreeNode
+    TreeNode,
+    Node
 )
 __all__.extend(misc_util.__all__)