Cedar - Maria O.

linked_list/linked_list.py

@@ -1,5 +1,8 @@
 
 # Defines a node in the singly linked list
+from calendar import c
+
+
 class Node:
 
     def __init__(self, value, next_node = None):
@@ -9,71 +12,150 @@ 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 not self.head:
+            return None
+        else:
+            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
+        # get head and iterate through nodes until right value
+        current_node = self.head
+        if not current_node:
+            return False
+
+        while current_node.value != value:
+            if current_node.next:
+                current_node = current_node.next
+            else:
+                return False
+        else:
+            return True
 
     # 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
+        # start counter, go through list, if next increase counter
+        current_node = self.head
+        length = 0
+        while current_node:
+            length += 1
+            if current_node.next:
+                current_node = current_node.next
+            else:
+                return length
+        else:
+            return length
+
 
     # 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
+        # use counter, when counter matches index, return
+        current_node = self.head
+        counter = 0
+        if not current_node:
+            return None
+        elif counter == index:
+            return current_node.value
+        while counter != index:
+            if current_node.next:
+                current_node = current_node.next
+            else:
+                return None
+            counter += 1
+        else:
+            return current_node.value
 
     # 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
+        current_node = self.head
+        if not current_node:
+            return None
+        while current_node.next:
+            current_node = current_node.next
+        else:
+            return current_node.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
+        current_node = self.head
+        new_node = Node(value)
+        if not current_node:
+            self.head = new_node
+            return
+            # self.add_first(value)
+            # return
+        while current_node.next:
+            current_node = current_node.next
+        else:
+            current_node.next = new_node
 
     # method to return the max value in the linked list
     # returns the data value and not the node
+    # Time Complexity: O(n)
+    # Space Complexity: O(1)
     def find_max(self):
-        pass
+        current_node = self.head
+        if not current_node:
+            return None
+        current_max = -900000000
+        while current_node != None:
+            if current_max < current_node.value:
+                current_max = current_node.value
+            current_node = current_node.next
+        return current_max
+
 
     # method to delete the first node found with specified value
-    # Time Complexity: ?
-    # Space Complexity: ?
+    # Time Complexity: O(n)
+    # Space Complexity: O(1)
     def delete(self, value):
-        pass
+        current_node = self.head
+        if not current_node:
+            return None
+        while current_node:
+            if current_node.value == value:
+                self.head = current_node.next
+                break
+            elif current_node.next.value == value:
+                current_node.next = current_node.next.next
+                break
+            else:
+                current_node = current_node.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
@@ -86,11 +168,22 @@ def visit(self):
 
     # 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
-
+        current_node = self.head
+        previous_node = None
+        next_node = current_node.next
+
+        while current_node:
+            current_node.next = previous_node
+            previous_node = current_node
+            current_node = next_node
+            if next_node:
+                next_node = next_node.next
+
+        self.head = previous_node
+
     ## Advanced/ Exercises
     # returns the value at the middle element in the singly linked list
     # Time Complexity: ?