Nourhan - Spruce - C16

linked_list/linked_list.py

@@ -1,75 +1,135 @@
-
-# Defines a node in the singly linked list
 class Node:
+    '''
+    Defines a node in the singly linked list
+    '''
 
-    def __init__(self, value, next_node = None):
+    def __init__(self, value, next_node=None):
         self.value = value
         self.next = next_node
 
-# Defines the singly linked list
+
 class LinkedList:
+    '''
+    Defines the singly linked list
+    '''
+
     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 not None:
+            return self.head.value
+        else:
+            return None
 
     # 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, next_node=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_node = self.head
+        while current_node is not None:
+            if current_node.value == value:
+                return True
+            current_node = current_node.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_node = self.head
+        length = 0
+        while current_node is not None:
+            length += 1
+            current_node = current_node.next
+        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
+        current_node = self.head
+        current_index = 0
+        while current_node is not None:
+            if index == current_index:
+                return current_node.value
+            current_node = current_node.next
+            current_index += 1
+        return None
 
     # 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
+        while current_node is not None:
+            if current_node.next is None:
+                return current_node.value
+            current_node = current_node.next
+        return None
 
     # 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
+        last_node = self.head
+        while last_node is not None:
+            if last_node.next is None:
+                break
+            last_node = last_node.next
+
+        if last_node is not None:
+            last_node.next = Node(value)
+        else:
+            self.head = Node(value)
 
     # method to return the max value in the linked list
     # returns the data value and not the node
     def find_max(self):
-        pass
+        current_node = self.head
+        if current_node is None:
+            return None
+        max_val = current_node.value
+        while current_node is not None:
+            max_val = max(current_node.value, max_val)
+            current_node = current_node.next
+        return max_val
 
     # 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
+        # Head has the value to delete
+        if self.head is not None\
+                and self.head.value == value:
+            self.head = self.head.next
+            return
+
+        current_node = self.head
+        # value to delete is in not head
+        while current_node is not None:
+            next_node = current_node.next
+            if next_node is not None\
+                    and next_node.value == value:
+                current_node.next = next_node.next
+                return
+            current_node = next_node
 
     # method to print all the values in the linked list
     # Time Complexity: ?
@@ -81,20 +141,36 @@ def visit(self):
         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(n)
     def reverse(self):
-        pass
-
+        node_list = []
+        current_node = self.head
+        while current_node is not None:
+            node_list.append(current_node)
+            current_node = current_node.next
+
+        for index in range(len(node_list)-1, 0, -1):
+            try:
+                node_list[index].next = node_list[index-1]
+            except IndexError:
+                node_list[index].next = None
+
+        try:
+            self.head = node_list[-1]
+        except IndexError:
+            self.head = None
+
     ## Advanced/ Exercises
     # returns the value at the middle element in the singly linked list
     # Time Complexity: ?
     # Space Complexity: ?
+
     def find_middle_value(self):
         pass
 
@@ -125,4 +201,4 @@ def create_cycle(self):
         while current.next != None:
             current = current.next
 
-        current.next = self.head # make the last node link to first node
+        current.next = self.head  # make the last node link to first node