Add implementation of array binary tree.

Rewrite the tree serialization and deserialization methods.
Add applications of array and linked list.

codes/python/modules/list_node.py

@@ -0,0 +1,39 @@
+"""
+File: list_node.py
+Created Time: 2021-12-11
+Author: Krahets (krahets@163.com)
+"""
+
+
+class ListNode:
+    """Definition for a singly-linked list node"""
+
+    def __init__(self, val: int):
+        self.val: int = val  # 节点值
+        self.next: ListNode | None = None  # 后继节点引用
+
+
+def list_to_linked_list(arr: list[int]) -> ListNode | None:
+    """Generate a linked list with a list"""
+    dum = head = ListNode(0)
+    for a in arr:
+        node = ListNode(a)
+        head.next = node
+        head = head.next
+    return dum.next
+
+
+def linked_list_to_list(head: ListNode | None) -> list[int]:
+    """Serialize a linked list into an array"""
+    arr: list[int] = []
+    while head:
+        arr.append(head.val)
+        head = head.next
+    return arr
+
+
+def get_list_node(head: ListNode | None, val: int) -> ListNode | None:
+    """Get a list node with specific value from a linked list"""
+    while head and head.val != val:
+        head = head.next
+    return head