Paper - Malakhova K.

linked_list/linked_list.py

@@ -16,80 +16,142 @@ def __init__(self):
     # Time Complexity: ?
     # Space Complexity: ?
     def get_first(self):
-        pass
+        if self.head == 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
+        new_node = Node(value)
+        new_node.next = self.head
+        self.head = new_node
 
     # 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 != None:
+            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
+        counter = 0
+        current  = self.head
+        while current != None:
+            current = current.next
+            counter += 1
+        return counter
 
     # 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: O(1)
     def get_at_index(self, index):
-        pass
+        if self.length() < index:
+            return None
+        current = self.head
+        current_index = 0
+        while current != None:
+            if current_index == index:
+                return current.value
+            current = current.next
+            current_index += 1
 
     # 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: O(n)
+    # Space Complexity: O(1)
     def get_last(self):
-        pass
+        if self.head == None:
+            return None
+        current = self.head
+        while current.next != None:
+            current = current.next
+        return current.value
 
     # method that inserts a given value as a new last node in the linked list
-    # Time Complexity: ?
-    # Space Complexity: ?
+    # Time Complexity: O(n)
+    # Space Complexity: O(1)
     def add_last(self, value):
-        pass
+        new_node = Node(value)
+        if self.head == None:
+            self.head = new_node
+            return 
+        current = self.head
+        while current.next != None:
+            current = current.next
+        current.next = 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 == None:
+            return None
+        max_value = self.head.value
+        current = self.head.next
+        while current != None:
+            if max_value < current.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: O(1)
+    # Space Complexity: O(n)
     def delete(self, value):
-        pass
+        curr = self.head
+        prev = None
+        if curr == None:
+            return None
+        while curr:
+            if curr.value == value:
+                # if not head of list
+                if prev:
+                    prev.next = curr.next
+                else:
+                    self.head = curr.next
+            prev = curr
+            curr = curr.next
 
     # 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
-
         while current:
             helper_list.append(str(current.value))
             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: ?
+    # Time Complexity: O(n)
+    # Space Complexity: O(1)
     def reverse(self):
-        pass
+        prev = None
+        current = self.head
+        next = None
+
+        while current != None:
+            next = current.next
+            current.next = prev
+            prev = current
+            current = next
+        self.head = prev
 
     ## Advanced/ Exercises
     # returns the value at the middle element in the singly linked list