From e239196065db2dba0b33217d20a704c9ffeff021 Mon Sep 17 00:00:00 2001
From: Stefan Harmuth <stefan.harmuth@docomodigital.com>
Date: Fri, 14 Jan 2022 10:19:30 +0100
Subject: [PATCH] starting linked lists

---
 tools/lists.py | 167 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 167 insertions(+)
 create mode 100644 tools/lists.py

diff --git a/tools/lists.py b/tools/lists.py
new file mode 100644
index 0000000..5905196
--- /dev/null
+++ b/tools/lists.py
@@ -0,0 +1,167 @@
+from dataclasses import dataclass
+from typing import Any, Union
+
+
+@dataclass
+class Node:
+    value: Any
+    next: 'Node' = None
+    prev: 'Node' = None
+
+
+class Stack:
+    _tail: Node = None
+    size: int = 0
+
+    def push(self, obj: Any):
+        self._tail = Node(obj, self._tail)
+        self.size += 1
+
+    def pop(self) -> Any:
+        if self._tail is None:
+            raise ValueError('No more objects on stack')
+
+        res = self._tail.value
+        self._tail = self._tail.next
+        self.size -= 1
+        return res
+
+    def peek(self) -> Any:
+        if self._tail is None:
+            raise ValueError('No more objects on stack')
+
+        return self._tail.value
+
+    def __contains__(self, obj: Any) -> bool:
+        x = self._tail
+        while x.value != obj and x.next is not None:
+            x = x.next
+
+        return x.value == obj
+
+
+class Queue:
+    pass
+
+
+class LinkedList:
+    _head: Union[Node, None] = None
+    _tail: Union[Node, None] = None
+    size: int = 0
+
+    def _append(self, obj: Any):
+        node = Node(obj)
+        if self._head is None:
+            self._head = node
+
+        if self._tail is None:
+            self._tail = node
+        else:
+            self._tail.next = node
+            node.prev = self._tail
+            self._tail = node
+
+        self.size += 1
+
+    def _insert(self, index: int, obj: Any):
+        i_node = Node(obj)
+        node = self._get_node(index)
+
+        i_node.prev, i_node.next = node.prev, node
+        node.prev = i_node
+        if node.prev is not None:
+            node.prev.next = i_node
+
+        if index == 0:
+            self._head = i_node
+
+        if index == self.size - 1:
+            self._tail = i_node
+
+        self.size += 1
+
+    def _get_node(self, index: int) -> Node:
+        if abs(index) >= self.size:
+            raise IndexError("index out of bounds")
+
+        if index < 0:
+            index = self.size + index
+
+        if index <= self.size // 2:
+            x = 0
+            node = self._head
+            while x < index:
+                x += 1
+                node = node.next
+        else:
+            x = self.size - 1
+            node = self._tail
+            while x > index:
+                x -= 1
+                node = node.prev
+
+        return node
+
+    def _get(self, index: int) -> Any:
+        return self._get_node(index).value
+
+    def _pop(self, index: int = None) -> Any:
+        if self.size == 0:
+            raise IndexError("pop from empty list")
+
+        if index is None:  # pop from the tail
+            node = self._tail
+            if self.size > 1:
+                self._tail = self._tail.prev
+                self._tail.next = None
+            else:
+                self._head = None
+                self._tail = None
+
+            ret = node.value
+        elif index == 0:  # pop from the head
+            node = self._head
+            if self.size > 1:
+                self._head = self._head.next
+                self._head.prev = None
+            else:
+                self._head = None
+                self._tail = None
+
+            ret = node.value
+        else:
+            node = self._get_node(index)
+            if node.prev is not None:
+                node.prev.next = node.next
+            if node.next is not None:
+                node.next.prev = node.prev
+            node.prev = None
+            node.next = None
+            ret = node.value
+
+        self.size -= 1
+        return ret
+
+    def append(self, obj: Any):
+        self._append(obj)
+
+    def insert(self, index: int, obj: Any):
+        self._insert(index, obj)
+
+    def get(self, index: int) -> Any:
+        return self._get(index)
+
+    def pop(self, index: int = None) -> Any:
+        return self._pop(index)
+
+    def debug(self):
+        print("head:", self._head)
+        print("tail:", self._tail)
+        if self.size > 0:
+            x = 0
+            o = self._head
+            print(x, o.value)
+            while o.next is not None:
+                x += 1
+                o = o.next
+                print(x, o.value)