Feature/daily problem

leetcode/Delete the Middle Node of a Linked List/Delete the Middle Node of a Linked List.py

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+from typing import Optional
+
+# Definition for singly-linked list.
+class ListNode:
+    def __init__(self, val=0, next=None):
+        self.val = val
+        self.next = next
+
+class Solution:
+    def deleteMiddle(self, head: Optional[ListNode]) -> Optional[ListNode]:
+        if not head or not head.next:
+            return None
+
+        # Dummy node to handle edge cases
+        dummy = ListNode(0, head)
+        slow = dummy
+        fast = head
+
+        # Move fast twice as fast as slow
+        while fast and fast.next:
+            slow = slow.next
+            fast = fast.next.next
+
+        # Delete the middle node
+        slow.next = slow.next.next
+
+        return dummy.next

leetcode/Maximum Twin Sum of a Linked List/Maximum Twin Sum of a Linked List.py

@@ -0,0 +1,33 @@
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+
+class Solution:
+    def pairSum(self, head: Optional[ListNode]) -> int:
+        # Find middle using slow and fast pointers
+        slow = fast = head
+        while fast and fast.next:
+            slow = slow.next
+            fast = fast.next.next
+
+        # Reverse the second half
+        prev = None
+        curr = slow
+        while curr:
+            nxt = curr.next
+            curr.next = prev
+            prev = curr
+            curr = nxt
+
+        # Now prev is the head of reversed second half
+        max_sum = 0
+        first = head
+        second = prev
+        while second:
+            max_sum = max(max_sum, first.val + second.val)
+            first = first.next
+            second = second.next
+
+        return max_sum