python单链表判断是否是回文字符串

python/06_linkedlist/palindrome.py

@@ -0,0 +1,54 @@
+"""
+    check a single-linked list whether a palindrome
+"""
+
+import sys
+# 引用当前文件夹下的single_linked_list
+sys.path.append('singly_linked_list')
+from singly_linked_list import SinglyLinkedList
+
+def reverse(head):
+    reverse_head = None
+    while head:
+        next = head._next
+        head._next = reverse_head
+        reverse_head = head
+        head = next
+
+    return reverse_head
+
+def is_palindrome(l):
+    l.print_all()
+    slow = l._head
+    fast = l._head
+    position = 0
+    while fast and fast._next:
+        slow = slow._next
+        fast = fast._next._next
+        position += 1
+
+    reverse_node = reverse(slow)
+    head_node = l._head
+    is_palin = True
+    while (head_node and reverse_node):
+        if (head_node.data == reverse_node.data):
+            head_node = head_node._next
+            reverse_node = reverse_node._next
+        else:
+            is_palin = False
+            break
+
+    return is_palin
+
+if __name__ == '__main__':
+    # the result should be False, True, True, True, True
+    test_str_arr = ['ab', 'aa', 'aba', 'abba', 'abcba']
+    for str in test_str_arr:
+        l = SinglyLinkedList()
+        for i in str:
+            l.insert_value_to_head(i)
+
+        print(is_palindrome(l))
+
+
+