From 7c9090f292520ec9f5209a2574010031225c225b Mon Sep 17 00:00:00 2001
From: Benjamin Adovasio <benjamin@adovasio.com>
Date: Sun, 15 Mar 2026 15:20:18 -0400
Subject: [PATCH] added template code for project 4

---
 Project 4/LinkedList Template.py | 166 +++++++++++++++++++++++++++++++
 Project 5/Stack.py               |   2 +-
 2 files changed, 167 insertions(+), 1 deletion(-)
 create mode 100644 Project 4/LinkedList Template.py

diff --git a/Project 4/LinkedList Template.py b/Project 4/LinkedList Template.py
new file mode 100644
index 0000000..f314126
--- /dev/null
+++ b/Project 4/LinkedList Template.py	
@@ -0,0 +1,166 @@
+######################################
+# DCS 229 -- Linked List
+# Linked List implementation
+# Date:
+# Name:
+# Resources Used:
+##########################################
+from __future__ import annotations
+
+# https://docs.python.org/3/tutorial/errors.html#user-defined-exceptions
+# Want to define our own custom Exception class...
+
+class EmptyError(Exception):
+    def __init__(self, message: str) -> None:
+        super().__init__(message)
+        self.message = message
+
+class Node[T]:
+    ''' class to implement a single node object in a singly-linked
+        linked list '''
+    def __init__(self, data: T):
+        self.data = data
+        self.next = None  # points to another Node object
+
+    def get_data(self) -> T:
+        return self.data
+    
+    def set_data(self, value: T) -> None:
+        self.data = value
+
+    def get_next(self) -> Node[T]:
+        return self.next
+    
+    def set_next(self, next_node: Node[T]) -> None:
+        self.next = next_node
+
+class LinkedList[T]:
+    ''' class to implement a singly-linked linked list '''
+
+    def __init__(self) -> None:
+        self.head = None   # the head pointer in the linked list
+        self.size = 0
+
+    def __len__(self) -> int:
+        ''' returns the number of nodes in the linked list
+        
+        Returns:
+            int - representing the number of nodes in the list
+        '''
+        pass
+
+
+    def insert_head(self, value: T) -> None:
+        ''' adds the given T-type data value to the front of the linked list
+        Parameters:
+            value: a type T data item to be included as the data in the inserted Node
+        Returns:
+            nothing
+        '''
+
+        ## YOUR CODE HERE ##
+       
+        pass
+
+    def insert_tail(self, value: T) -> None:
+        ''' adds the given T-type data value to the end of the linked list
+        Parameters:
+            value: a type T data item to be included as the data in the inserted Node
+        Returns:
+            nothing
+        '''
+
+        ## YOUR CODE HERE ##
+
+        pass
+
+    def remove_head(self) -> T:
+        ''' removes the first Node in the linked list, returning the data item
+            inside that Node...  Remember to handle the special case of an 
+            empty list (what should the head pointers be in that case?)
+            and remember to update the head pointer when appropriate.
+        Returns:
+            a T type data item extracted from the removed Node
+        Raises:
+            EmptyError exception if list is empty
+        '''
+
+        # raise an error if list is empty
+        # https://docs.python.org/3/tutorial/errors.html#user-defined-exceptions
+        if self.size == 0:
+            raise EmptyError("Cannot remove from an empy list")
+
+
+        ## YOUR CODE HERE ##
+
+        pass
+
+    def remove_tail(self) -> T:
+        ''' removes the last Node in the linked list, returning the data item
+            inside that Node...  Remember to handle the special case of an 
+            empty list
+
+        Returns:
+            a T type data item extracted from the removed Node
+        Raises:
+            EmptyError exception if list is empty
+        '''
+        # raise an error if list is empty
+        if self.size == 0:
+            raise EmptyError("Cannot remove from an empy list")
+    
+        ## YOUR CODE HERE ##
+
+        pass
+
+ 
+
+
+    def __str__(self):
+        ''' returns a str representation of the linked list data
+        Returns:
+            an str representation of the linked list, showing head pointer
+                and data tiems
+        '''
+        str_ = "head->"
+
+        # start out at the head Node, and walk through Node by Node until we
+        # reach the end of the linked list (i.e., the ._next entry is None)
+        ptr_ = self.head
+        while ptr_ is not None:
+            str_ += "[" + str(ptr_.get_data()) + "]->" 
+            ptr_ = ptr_.get_next()  # move ptr_ to the next Node in the linked list
+
+        if self.head != None:
+            str_ = str_[:-2]  # remove trailing "->"
+        str_ += "<-tail"
+        return str_
+
+def main():
+    # create a LinkedList and try out some various adds and removes
+    ll = LinkedList()
+    try:
+        ll.remove_head()
+    except EmptyError as err:
+        print(err)
+
+    ll.insert_head(8)
+    assert len(ll) == 1
+    removed = ll.remove_head()
+    assert removed == 8
+    assert len(ll) == 0
+
+    ll.insert_tail(6)
+    ll.insert_tail(7)
+    ll.insert_tail(5)
+    print(ll)
+    assert len(ll) == 3
+
+    removed = ll.remove_tail()
+    assert removed == 5
+    assert len(ll) == 2
+
+    # ADD MORE TESTS
+    
+if __name__ == "__main__":
+    main()
\ No newline at end of file
diff --git a/Project 5/Stack.py b/Project 5/Stack.py
index ea0fc2d..29d8e01 100644
--- a/Project 5/Stack.py	
+++ b/Project 5/Stack.py	
@@ -3,7 +3,7 @@
 # Stack data structure implemented with Linked List
 # Date:
 # Name:
-# Resources Used:
+# Resources Used: LinkedList.py from Project 4
 ##########################################