Maple: Sabrina Lauredan

linked_list/linked_list.py

@@ -1,5 +1,8 @@
 
 # Defines a node in the singly linked list
+from threading import currentThread
+
+
 class Node:
 
     def __init__(self, value, next_node = None):
@@ -9,71 +12,126 @@ def __init__(self, value, next_node = None):
 # Defines the singly linked list
 class LinkedList:
     def __init__(self):
-      self.head = None # keep the head private. Not accessible outside this class
+        self.head = None # keep the head private. Not accessible outside this class
 
     # returns the value in the first node
     # returns None if the list is empty
-    # Time Complexity: ?
-    # Space Complexity: ?
+    # Time Complexity: O(1)
+    # Space Complexity: O(1)
     def get_first(self):
-        pass
+        if self.head is None:
+            return None
+
+        return self.head.value
 
 
     # method to add a new node with the specific data value in the linked list
     # insert the new node at the beginning of the linked list
-    # Time Complexity: ?
-    # Space Complexity: ?
+    # Time Complexity: O(1)
+    # Space Complexity: O(1)
     def add_first(self, value):
-        pass
+        self.head = Node(value, self.head)
+
 
     # method to find if the linked list contains a node with specified value
     # returns true if found, false otherwise
-    # Time Complexity: ?
-    # Space Complexity: ?
+    # Time Complexity: O(n)
+    # Space Complexity: O(1)
     def search(self, value):
-        pass
-
+        current = self.head
+        while current:
+            if current.value == value:
+                return True
+            current = current.next
+        return False 
+
     # method that returns the length of the singly linked list
-    # Time Complexity: ?
-    # Space Complexity: ?
+    # Time Complexity: O(n)
+    # Space Complexity: O(1)
     def length(self):
-        pass
+        current = self.head
+        lenght_of_list = 0
+        while current != None:
+            lenght_of_list += 1
+            current = current.next
+        return lenght_of_list
 
     # method that returns the value at a given index in the linked list
     # index count starts at 0
     # returns None if there are fewer nodes in the linked list than the index value
-    # Time Complexity: ?
-    # Space Complexity: ?
+    # Time Complexity:  O(n)
+    # Space Complexity: 0(1)
     def get_at_index(self, index):
-        pass
+        current_node = self.head
+        current_index = 0
+        while current_node != None: 
+            if current_index == index:
+                return current_node.value
+            current_index += 1
+            current_node = current_node.next
+        return current_node
 
     # method that returns the value of the last node in the linked list
     # returns None if the linked list is empty
-    # Time Complexity: ?
-    # Space Complexity: ?
+    # Time Complexity: 0(1)
+    # Space Complexity: 0(1)
     def get_last(self):
-        pass
+        if self.length() is 0:
+            return None
+        return self.tail.value 
 
     # method that inserts a given value as a new last node in the linked list
-    # Time Complexity: ?
-    # Space Complexity: ?
+    # Time Complexity: 0(1)
+    # Space Complexity: 0(1)
     def add_last(self, value):
-        pass
+        if self.head is None:
+            self.head = Node(value)
+        else:
+            new_node = Node(value)
+            new_node.previous = self.tail
+            self.tail.next = new_node
+            self.tail = new_node
+
 
     # method to return the max value in the linked list
     # returns the data value and not the node
     def find_max(self):
-        pass
+        if self.head is None:
+            return None 
+
+        current = self.head
+        max_value = current.value
+        while current:
+            if current.value > max_value:
+                max_value = current.value
+            current = current.next
+        return max_value
 
     # method to delete the first node found with specified value
-    # Time Complexity: ?
-    # Space Complexity: ?
+    # Time Complexity: 0(n)
+    # Space Complexity: 0(1)
     def delete(self, value):
-        pass
+        if self.head is None:
+            return 
+        if value == 0:
+            self.head = self.head.next
+        index = 0
+        current = self.head
+        prev = self.head
+        temp = self.head
+        while current is not None:
+            if index == value:
+                temp = current.next
+                break
+            prev = current
+            current = current.next
+            index += 1
+        prev.next = temp
+        return prev
 
     # method to print all the values in the linked list
-    # Time Complexity: ?
-    # Space Complexity: ?
+    # Time Complexity: O(n)
+    # Space Complexity: O(n)
     def visit(self):
         helper_list = []
         current = self.head
@@ -83,46 +141,3 @@ def visit(self):
             current = current.next
 
         print(", ".join(helper_list))
-
-    # method to reverse the singly linked list
-    # note: the nodes should be moved and not just the values in the nodes
-    # Time Complexity: ?
-    # Space Complexity: ?
-    def reverse(self):
-        pass
-
-    ## Advanced/ Exercises
-    # returns the value at the middle element in the singly linked list
-    # Time Complexity: ?
-    # Space Complexity: ?
-    def find_middle_value(self):
-        pass
-
-    # find the nth node from the end and return its value
-    # assume indexing starts at 0 while counting to n
-    # Time Complexity: ?
-    # Space Complexity: ?
-    def find_nth_from_end(self, n):
-        pass
-
-    # checks if the linked list has a cycle. A cycle exists if any node in the
-    # linked list links to a node already visited.
-    # returns true if a cycle is found, false otherwise.
-    # Time Complexity: ?
-    # Space Complexity: ?
-    def has_cycle(self):
-        pass
-
-    # Helper method for tests
-    # Creates a cycle in the linked list for testing purposes
-    # Assumes the linked list has at least one node
-    def create_cycle(self):
-        if self.head == None:
-            return
-
-        # navigate to last node
-        current = self.head
-        while current.next != None:
-            current = current.next
-
-        current.next = self.head # make the last node link to first node