Wangdi tenzing

queue/queue.py

@@ -13,16 +13,114 @@
 Stretch: What if you could only use instances of your Stack class to implement the Queue?
          What would that look like? How many Stacks would you need? Try it!
 """
+
+# class Node:
+#     def __init__(self, value=None, next_node=None):
+#         self.value=value
+#         self.next_node=next_node
+
+#     def get_value(self):
+#         return self.value
+
+#     def get_next_node(self):
+#         return self.next_node
+
+#     def set_next_node(self,next_new):
+#         self.next_node=next_new
+
+
+# class LinkedList:
+#     def __init__(self):
+#         self.head=None
+#         self.tail=None
+
+#     def add_to_head(self,value):
+#         #create a new Node
+#         new_node=Node(value)
+#         if self.head is None:
+#             #update the head and tail attributes 
+#             self.head=new_node
+#             self.tail=new_node
+#         else:
+#             #set the next node of the new node to the head 
+#             new_node.set_next_node(self.head)
+#             #update the head attribute
+#             self.head=new_node
+
+#     def add_to_tail(self,value):
+#         #create a new node
+#         new_node=Node(value)
+#         # if the linked list is empty (case 1)
+#         if self.head is None:
+#             #update the head and tail attributes 
+#             self.head=new_node
+#             self.tail=new_node
+#         # the linked list is not empty (case 2)
+#         else:
+#             #update the next node of the tail 
+#             self.tail.set_next_node(new_node)
+#             #update self.tail
+#             self.tail=new_node
+
+#     def remove_head(self):
+#         # if it is an empty list (case1)
+#         if self.head is None:
+#             return None 
+#         # else return the old value of the head 
+#         else:
+#             ret_value=self.head.get_value()
+#             #list with one element 
+#             if self.head ==self.tail:
+#                 self.head =None
+#                 self.tail=None
+#             else:
+#                 self.head=self.head.get_next_node()
+#                 return ret_value
+
+#     def remove_tail(self):
+#         # if it is an empty list 
+#         if self.head is None:
+#             return None
+#         else:
+#             ret_value=self.tail.get_value()
+#             #list with one element 
+#             if self.head ==self.tail:
+#                 self.head =None
+#                 self.tail=None
+#             # if the list has more than 2 elements 
+#             else:
+#                 #if the next node is not the tail 
+#                 # assign the current_node to the next 
+#                 # set the current node to None by doing so the current node becomes the new tail 
+#                 current_node =self.head
+#                 while current_node.next_node is not self.tail:
+#                     current_node=current_node.next_node
+#                     current_node.set_next_node(None)
+#                     self.tail=current_node
+#                 return ret_value
+
+
+from singly_linked_list import LinkedList
+
+
+
+
 class Queue:
     def __init__(self):
         self.size = 0
-        # self.storage = ?
+        self.storage=LinkedList()
 
     def __len__(self):
-        pass
+        return self.size
 
     def enqueue(self, value):
-        pass
+        self.storage.add_to_tail(value)
+        self.size +=1
+        return self.storage
 
     def dequeue(self):
-        pass
+        if self.size >=1:
+           value=self.storage.remove_head()
+           self.size -=1
+           return value
+

queue/singly_linked_list.py

@@ -0,0 +1,115 @@
+# a  class that represents the individual elements in our LL
+class Node:
+    def __init__(self,value=None, next_node=None):
+        self.value=value
+        self.next_node=next_node
+
+    def get_value(self):
+        return self.value
+
+    def get_next_node(self):
+        return self.next_node
+
+    def set_next_node (self,new_next):
+        self.next_node=new_next
+
+class LinkedList:
+    def __init__(self):
+        #what attributes do we need to create a LinkedList ?
+        self.head=None
+        self.tail=None
+
+    def add_to_head(self,value):
+        #create a new Node
+        new_node=Node(value)
+        if self.head is None:
+           #update head and tail attributes 
+           self.head=new_node
+           self.tail=new_node
+        else:
+            #set next_node of my new Node to the head
+            new_node.set_next_node(self.head)
+            #update the head attribute
+            self.head=new_node
+
+
+
+
+    def add_to_tail(self,value):
+        #1. create a node from the value 
+        new_node=Node(value)
+        # Whats the rule we want to set to indicate that the linked list is empty?
+        # wouldn't it be better to check the head ? 
+
+        #case1: consider the LL being empty 
+
+        if self.head is None:
+            #update the head and tail attributes
+            self.head=new_node
+            self.tail=new_node
+        #case2 : consider the LL not being empty 
+        else:
+
+            self.tail.set_next_node(new_node)
+            #reassign self.tail to refer to the new node 
+            self.tail=new_node
+
+    def remove_head(self):
+         # case1: empty list
+        if self.head is None:
+            return None
+         #  return the value of the old head
+        else:
+            old_head=self.head.get_value()
+            if self.head==self.tail:
+                self.head==None
+                self.tail==None
+            else:
+                self.head=self.head.get_next_node()
+                return old_head
+
+    def remove_tail(self):
+        # if we have an emoty list we dont have to remove anything 
+        if self.head is None :
+            return None
+        #else return value of the old head
+        else:
+            ret_value=self.tail.get_value()
+
+        #if we have a list with one element 
+        if self.head==self.tail:
+           self.head=None
+           self.tail=None
+
+        #list with two elements 
+        else:
+             # if current.next node is not the tail 
+             # assign current to current.next.. then you set it to None making that the new tail 
+             # return the current value
+
+            cur_node=self.head
+            while cur_node.get_next_node()is not self.tail:
+                cur_node=cur_node.get_next_node()
+        # keep going 
+        #update pointer of temp node (prev_tail)None 
+            cur_node.set_next_node(None)
+            self.tail=cur_node
+        #return value 
+        return ret_value
+
+    def contains(self,value):
+        cur_node=self.head
+        while cur_node is not None:
+            # if value exists
+            if cur_node.get_value()==value:
+                return True
+
+        return False
+
+
+
+
+
+
+
+

singly_linked_list/singly_linked_list.py

@@ -0,0 +1,116 @@
+# a  class that represents the individual elements in our LL
+class Node:
+    def __init__(self,value=None, next_node=None):
+        self.value=value
+        self.next_node=next_node
+
+    def get_value(self):
+        return self.value
+
+    def get_next_node(self):
+        return self.next_node
+
+    def set_next_node (self,new_next):
+        self.next_node=new_next
+
+class LinkedList:
+    def __init__(self):
+        #what attributes do we need to create a LinkedList ?
+        self.head=None
+        self.tail=None
+
+    def add_to_head(self,value):
+        #create a new Node
+        new_node=Node(value)
+        if self.head is None:
+           #update head and tail attributes 
+           self.head=new_node
+           self.tail=new_node
+        else:
+            #set next_node of my new Node to the head
+            new_node.set_next_node(self.head)
+            #update the head attribute
+            self.head=new_node
+
+
+
+
+    def add_to_tail(self,value):
+        #1. create a node from the value 
+        new_node=Node(value)
+        # Whats the rule we want to set to indicate that the linked list is empty?
+        # wouldn't it be better to check the head ? 
+
+        #case1: consider the LL being empty 
+
+        if self.head is None:
+            #update the head and tail attributes
+            self.head=new_node
+            self.tail=new_node
+        #case2 : consider the LL not being empty 
+        else:
+
+            self.tail.set_next_node(new_node)
+            #reassign self.tail to refer to the new node 
+            self.tail=new_node
+
+    def remove_head(self):
+         # case1: empty list
+        if self.head is None:
+            return None
+         #  return the value of the old head
+        else:
+            old_head=self.head.get_value()
+            if self.head==self.tail:
+                self.head=None
+                self.tail=None
+                return old_head
+            else:
+                self.head=self.head.get_next_node()
+                return old_head
+
+    def remove_tail(self):
+        # if we have an emoty list we dont have to remove anything 
+        if self.head is None :
+            return None
+        #else return value of the old head
+        else:
+            ret_value=self.tail.get_value()
+
+        #if we have a list with one element 
+        if self.head==self.tail:
+           self.head=None
+           self.tail=None
+
+        #list with two elements 
+        else:
+             # if current.next node is not the tail 
+             # assign current to current.next.. then you set it to None making that the new tail 
+             # return the current value
+
+            cur_node=self.head
+            while cur_node.get_next_node()is not self.tail:
+                cur_node=cur_node.get_next_node()
+        # keep going 
+        #update pointer of temp node (prev_tail)None 
+            cur_node.set_next_node(None)
+            self.tail=cur_node
+        #return value 
+        return ret_value
+
+    def contains(self,value):
+        cur_node=self.head
+        while cur_node is not None:
+            # if value exists
+            if cur_node.get_value()==value:
+                return True
+
+        return False
+
+
+
+
+
+
+
+

stack/stack.py

@@ -13,13 +13,16 @@
 class Stack:
     def __init__(self):
         self.size = 0
-        # self.storage = ?
+        self.storage = []
 
     def __len__(self):
-        pass
+        return len(self.storage)
 
     def push(self, value):
-        pass
+        return self.storage.append(value)
 
     def pop(self):
-        pass
+        if len(self.storage)==0:
+            return None
+        else:
+            return self.storage.pop()