148 Sort List.py

Author: peihenglyu

148 Sort List.py

@@ -10,10 +10,72 @@ def sortList(self, head):
         :type head: ListNode
         :rtype: ListNode
         """
-        list = []
-        poi = head
-        while poi:
-            list.append(poi)
+        if not head or not head.next:
+            return head
+
+
+        def merge(head_1, head_2):
+            dummy = ListNode()
+            ptr = dummy
+            while head_1 or head_2:
+                if not head_1:
+                    ptr.next = head_2
+                    break
+                elif not head_2:
+                    ptr.next = head_1
+                    break
+                elif head_1.val > head_2.val:
+                    ptr.next = head_2
+                    head_2 = head_2.next
+                    ptr = ptr.next
+                else:
+                    ptr.next = head_1
+                    head_1 = head_1.next
+                    ptr = ptr.next
+            return dummy.next
 
+        def solver(head):
+            if not head.next:
+                    return head
+            if not head.next.next:
+                if head.val > head.next.val:
+                    new_head = head.next
+                    head.next = None
+                    new_head.next = head
+                    return new_head
+                else:
+                    head.next.next = None
+                    return head
+            else:
+                fast_ptr = head
+                slow_ptr = head
+                while fast_ptr:
+                    fast_ptr = fast_ptr.next
+                    if fast_ptr:
+                        fast_ptr = fast_ptr.next
+                        slow_ptr = slow_ptr.next
+                
+                temp = slow_ptr.next
+                slow_ptr.next = None
+                    
+                return merge(solver(head), solver(temp))
+        
+        return solver(head)
+                
+
+head = ListNode(-1,ListNode(5,ListNode(3,ListNode(4,ListNode(0)))))
+head_2 = ListNode(4,ListNode(2,ListNode(1,ListNode(3))))
+
+obj = Solution()
+
+def print_LL(head):
+    s = []
+    while head:
+        s.append(head.val)
+        head = head.next
+    print(s)
+
+print_LL(obj.sortList(head))
+print_LL(obj.sortList(head_2))