solves linked list cycle

Author: anishLearnsToCode

README.md

@@ -42,7 +42,7 @@
 | 122 | [Best Time to Buy and Sell Stocks II](https://leetcode.com/problems/best-time-to-buy-and-sell-stock-ii) | Easy | [![Java](https://img.icons8.com/color/40/000000/java-coffee-cup-logo.png)](src/BestTimeToBuyAndSellStockII.java) [![Python](https://img.icons8.com/color/35/000000/python.png)](python/best_time_to_buy_and_sell_stock_ii.py) | 
 | 125 | [Valid Palindrome](https://leetcode.com/problems/valid-palindrome) | Easy | [![Java](https://img.icons8.com/color/40/000000/java-coffee-cup-logo.png)](src/ValidPalindrome.java) [![Python](https://img.icons8.com/color/35/000000/python.png)](python/valid_palindrome.py) |
 | 136 | [Single Number](https://leetcode.com/problems/single-number) | Easy | [![Java](https://img.icons8.com/color/40/000000/java-coffee-cup-logo.png)](src/SingleNumber.java) [![Python](https://img.icons8.com/color/35/000000/python.png)](python/single_number.py) | 
-| 141 | [Linked List Cycle](https://leetcode.com/problems/linked-list-cycle) | Easy | [![Java](https://img.icons8.com/color/40/000000/java-coffee-cup-logo.png)](src/LinkedListCycle.java) | 
+| 141 | [Linked List Cycle](https://leetcode.com/problems/linked-list-cycle) | Easy | [![Java](https://img.icons8.com/color/40/000000/java-coffee-cup-logo.png)](src/LinkedListCycle.java) [![Python](https://img.icons8.com/color/35/000000/python.png)](python/linked_list_cycle.py) | 
 | 155 | [Min Stack](https://leetcode.com/problems/min-stack) | Easy | [![Java](https://img.icons8.com/color/40/000000/java-coffee-cup-logo.png)](src/MinStack.java) |
 | 157 | [Read N Characters Given Read4](https://leetcode.com/problems/read-n-characters-given-read4) | Easy | |
 | 160 | [Intersection of Two Linked Lists](https://leetcode.com/problems/intersection-of-two-linked-lists) | Easy | [![Java](https://img.icons8.com/color/40/000000/java-coffee-cup-logo.png)](src/IntersectionOf2LinkedLists.java) |

python/linked_list_cycle.py

@@ -0,0 +1,21 @@
+# Definition for singly-linked list.
+class ListNode:
+    def __init__(self, x):
+        self.val = x
+        self.next = None
+
+
+class Solution:
+    def not_null(self, head: ListNode) -> bool:
+        return head is not None
+
+    def hasCycle(self, head: ListNode) -> bool:
+        if head is None:
+            return False
+        slow, fast = head, head.next
+        while self.not_null(slow) and self.not_null(fast) and self.not_null(slow.next) and self.not_null(fast.next):
+            if slow is fast:
+                return True
+            slow = slow.next
+            fast = fast.next.next
+        return False