feat(work): add Reverse Linked List solution

work/1/Easy/Linked List/206.reverse-linked-list.py

@@ -0,0 +1,57 @@
+"""
+206. Reverse Linked List
+Difficulty: Easy
+https://leetcode.com/problems/reverse-linked-list/
+
+──────────────────────────────────────────────────
+
+Given the head of a singly linked list, reverse the list, and return
+the reversed list.
+
+
+
+Example 1:
+
+Input: head = [1,2,3,4,5]
+Output: [5,4,3,2,1]
+
+Example 2:
+
+Input: head = [1,2]
+Output: [2,1]
+
+Example 3:
+
+Input: head = []
+Output: []
+
+
+
+Constraints:
+
+        • The number of nodes in the list is the range [0, 5000].
+
+        • -5000 <= Node.val <= 5000
+
+
+
+Follow up: A linked list can be reversed either iteratively or
+recursively. Could you implement both?
+"""
+
+
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def reverseList(self, head: Optional[ListNode]) -> Optional[ListNode]:
+        prev = None
+        curr = head
+        while curr:
+            next_ = curr.next
+            curr.next = prev
+            prev = curr
+            curr = next_
+        return prev