From bba0966e34bf5f026b5b027cad474b72dff73b04 Mon Sep 17 00:00:00 2001
From: Louie Tan <louietyj@gmail.com>
Date: Sat, 21 Oct 2017 01:33:19 +0800
Subject: [PATCH] LinkedList implementation

---
 utilities/python/linked_list.py | 73 +++++++++++++++++++++++++++++++++
 1 file changed, 73 insertions(+)
 create mode 100644 utilities/python/linked_list.py

diff --git a/utilities/python/linked_list.py b/utilities/python/linked_list.py
new file mode 100644
index 00000000..13a25b8b
--- /dev/null
+++ b/utilities/python/linked_list.py
@@ -0,0 +1,73 @@
+# Singly-Linked List
+#
+# The linked list is passed around as a variable pointing to the
+# root node of the linked list, or None if the list is empty.
+
+class LinkedListNode:
+    def __init__(self, value):
+        self.value = value
+        self.next = None
+
+def linked_list_append(linked_list, value):
+    '''Appends a value to the end of the linked list'''
+    node = linked_list
+    insert_node = LinkedListNode(value)
+    if not node:
+        return insert_node
+    while node.next:
+        node = node.next
+    node.next = insert_node
+    return linked_list
+
+def linked_list_insert_index(linked_list, value, index):
+    '''Inserts a value at a particular index'''
+    node = linked_list
+    insert_node = LinkedListNode(value)
+    
+    # Check if inserting at head
+    if index == 0:
+        insert_node.next = node
+        return insert_node
+
+    # Skip ahead
+    for _ in range(index - 1):
+        node = node.next
+        if not node:
+            raise ValueError
+    insert_node.next = node.next
+    node.next = insert_node
+    return linked_list
+
+def linked_list_delete(linked_list, value):
+    '''Deletes the first occurrence of a value in the linked list'''
+    node = linked_list
+    
+    # Check if deleting at head
+    if node.value == value:
+        return node.next
+
+    # Skip ahead
+    while node.next:
+        if node.next.value == value:
+            node.next = node.next.next
+            return linked_list
+        node = node.next
+    raise ValueError
+
+def linked_list_delete_index(linked_list, index):
+    '''Deletes the element at a particular index in the linked list'''
+    node = linked_list
+    
+    # Check if deleting at head
+    if index == 0:
+        return node.next
+
+    # Skip ahead
+    for _ in range(index - 1):
+        node = node.next
+        if not node:
+            raise ValueError
+    if not node.next:
+        raise ValueError
+    node.next = node.next.next
+    return linked_list