Remove duplicates from sorted list 2

arai60/remove_duplicates_from_sorted_list_2/phase1.py

@@ -0,0 +1,14 @@
+class Solution:
+    def deleteDuplicates(self, head: Optional[ListNode]) -> Optional[ListNode]:
+        dummy_head = ListNode(0)
+        current_head = dummy_head
+        skip_number = None
+        while head:
+            if head.next and head.val != head.next.val and head.val != skip_number:
+                current_head.next = ListNode(head.val)
+                current_head = current_head.next
+            elif head.next == None and head.val != skip_number:
+                current_head.next = ListNode(head.val)
+            skip_number = head.val
+            head = head.next
+        return dummy_head.next

arai60/remove_duplicates_from_sorted_list_2/phase2.py

@@ -0,0 +1,25 @@
+"""
+Reference:
+fhiyoさん: https://github.com/fhiyo/leetcode/pull/4/files
+nittocoさん: https://github.com/nittoco/leetcode/pull/9/files
+TORUさん: https://github.com/TORUS0818/leetcode/pull/6/files
+phase1の回答は, skip_numberという状態変数を持って条件を制御していくやりかただったが, 状態変数の扱いが難しいものになる恐れがあると考えた。
+あまり状態変数は持ちたくないものではあるので, 重複が見つかったらスキップというやり方を採用する。
+"""
+
+class Solution:
+    def deleteDuplicates(self, head: Optional[ListNode]) -> Optional[ListNode]:
+        def skip_duplicate_nodes(node):
+            while node.next and node.val == node.next.val:
+                node = node.next
+            return node
+        dummy_head = ListNode(-1)
+        current_node = dummy_head
+        while head:
+            if head.next and head.val == head.next.val:
+                head = skip_duplicate_nodes(head)
+            else:
+                current_node.next = ListNode(head.val)
+                current_node = current_node.next
+            head = head.next
+        return dummy_head.next

arai60/remove_duplicates_from_sorted_list_2/phase3.py

@@ -0,0 +1,16 @@
+class Solution:
+    def deleteDuplicates(self, head: Optional[ListNode]) -> Optional[ListNode]:
+        def skip_duplicated_nodes(head: Optional[ListNode]) -> Optional[ListNode]:
+            while head.next and head.val == head.next.val:
+                head = head.next
+            return head
+        dummy_head = ListNode(-1)
+        current_node = dummy_head
+        while head:
+            if head.next and head.val == head.next.val:
+                head = skip_duplicated_nodes(head)
+            else:
+                current_node.next = ListNode(head.val)
+                current_node = current_node.next
+            head = head.next
+        return dummy_head.next