From 6502708b29090426f7a4d38ac998cb52d8c661c7 Mon Sep 17 00:00:00 2001
From: Saad <saadbennmushtaq@gmail.com>
Date: Sat, 28 Apr 2018 23:08:03 -0500
Subject: [PATCH 1/2] Add algorithm for finding the starting node in a circular
 linked list.

---
 linkedlist/find_loop.py | 68 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 68 insertions(+)
 create mode 100644 linkedlist/find_loop.py

diff --git a/linkedlist/find_loop.py b/linkedlist/find_loop.py
new file mode 100644
index 000000000..5378ed2c0
--- /dev/null
+++ b/linkedlist/find_loop.py
@@ -0,0 +1,68 @@
+"""
+Find the start of a linked list loop
+
+Some constraints:
+* It is gonna be a singly linked list.
+* The parameter is not always gonna be a circular linked list.
+* Once the loop is found, return the node.
+
+Test Cases:
+* Empty list -> None
+* Not a circular linked list -> None
+	* One element
+	* Two or more elements
+* Circular linked list general case
+"""
+class LinkedList:
+
+	def __init__(self):
+		self.root = None
+
+	# Function to insert a new node at the beginning
+    def push(self, new_data):
+        new_node = Node(new_data)
+        new_node.next = self.head
+        self.head = new_node	
+
+	def find_loop_start(self):
+		if self.root is None or self.root.next is None:
+			return None
+
+		# Detect loop using Floyd’s Cycle detection algorithm 
+		slow = fast = self.root
+		while fast.root is not None:
+			slow = slow.next
+			fast = fast.next.next
+
+			if fast is None:
+				return None
+
+			if fast == slow:
+				break
+
+		# check for the starting node
+		slow = self.root
+		while slow != fast:
+			slow = slow.next
+			fast = fast.next
+
+			if fast is None:
+				return None
+		return slow	
+
+class Node:
+	
+	def __init__(self, _value):
+		self.value = _value
+		self.next = None							 
+
+
+linked_list = LinkedList()
+linked_list.push(10)
+linked_list.push(4)
+linked_list.push(15)
+linked_list.push(20)
+linked_list.push(50)
+
+# Make it a circular linked list
+linked_list.root.next.next.next.next.next = linked_list.root.next.next

From 282242192fb11c31aa0e4d6c9439ce0b358e4429 Mon Sep 17 00:00:00 2001
From: Sa'd <saadbennmushtaq@gmail.com>
Date: Sat, 28 Apr 2018 23:13:55 -0500
Subject: [PATCH 2/2] Fix indentation error

---
 linkedlist/find_loop.py | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/linkedlist/find_loop.py b/linkedlist/find_loop.py
index 5378ed2c0..d436ebe60 100644
--- a/linkedlist/find_loop.py
+++ b/linkedlist/find_loop.py
@@ -19,10 +19,10 @@ def __init__(self):
 		self.root = None
 
 	# Function to insert a new node at the beginning
-    def push(self, new_data):
-        new_node = Node(new_data)
-        new_node.next = self.head
-        self.head = new_node	
+	def push(self, new_data):
+		new_node = Node(new_data)
+		new_node.next = self.head
+		self.head = new_node	
 
 	def find_loop_start(self):
 		if self.root is None or self.root.next is None: