Merge branch 'main' of https://github.com/PacktPublishing/Hands-On-Data-Structures-and-Algorithms-with-Python-Third-Edition

Author: Sonawane-Karan26

Chapter01/chapter1.py

@@ -9,14 +9,14 @@
 ###############
 
 var = 13.2
-print(var)
+print(type(var))
 #13.2
 
 type (var)
 #<class ‘float’>
 
 var = "Now the type is string"
-print(var)
+print(type(var))
 
 type(var)
 #<class ‘str’>
@@ -36,6 +36,7 @@
 '''
 
 bool(False)
+print(bool(False))
 #False
 va1 = 0
 print(bool(va1))
@@ -50,9 +51,11 @@
 #True
 
 #### Strings
-Str1 = 'Hello how are you'
+str1 = 'Hello how are you'
 str2 = "Hello how are you"
 str3 = 'multiline'+'string';
+print(str1)
+print(str2)
 print(str3)
 
 f = 'data'
@@ -69,6 +72,22 @@
 print(3 * st)
 #'data.data.data.'
 
+###### Range ######
+
+print(list(range(10)))
+print(range(10))
+print(list(range(10)))
+print(range(1,10,2))
+print(list(range(1,10,2)))
+print(list(range(20,10,-2)))
+
+#[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
+#range(0, 10)
+#[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
+#range(1, 10, 2)
+#[1, 3, 5, 7, 9]
+#[20, 18, 16, 14, 12]
+
 
 ###### Lists ######
 
@@ -209,7 +228,7 @@
 if thirdList is Secondlist:
    print("Both are pointing to the same object")
 else:
-   print("Both are not pointing to the same object ") 
+   print("Both are not pointing to the same object") 
 '''
 Output:
 Both are equal	
@@ -223,12 +242,12 @@
 Firstlist = []
 Secondlist = []
 if Firstlist is not Secondlist:
-  print("Both are pointing to the different object")
+  print("Both Firstlist and Secondlist variables are the same object")
 else:
-  print("Both are not pointing to the different object ") 
+  print("Both Firstlist and Secondlist variables are not the same object") 
 
 #Output:
-# Both are pointing to the different object
+# Both Firstlist and Secondlist variables are the same object
 
 
 
@@ -461,6 +480,7 @@
 
 from collections import deque
 s = deque()        # Creates an empty deque
+print(s)
 my_queue = deque([1, 2, 'Name'])
 print(my_queue)
 #deque([1, 2, 'Name'])
@@ -506,9 +526,9 @@
 
 print(chain)
 #ChainMap({'data': 1, 'structure': 2}, {'python': 3, 'language': 4})
-print (list(chain.keys()))
+print(list(chain.keys()))
 #['python', 'language', 'data', 'structure']
-print (list(chain.values()))
+print(list(chain.values()))
 #[3, 4, 1, 2]
 print(chain["data"])
 #1

Chapter02/matrix_chain.py

@@ -5,10 +5,10 @@ def matrix_chain(mat, i, j):
         return 0     
     minimum_computations = sys.maxsize    
     for k in range(i, j):   
-        count = (MatrixChain(mat, i, k) + MatrixChain(mat, k+1, j)+ mat[i-1] * mat[k] * mat[j])     
+        count = (matrix_chain(mat, i, k) + matrix_chain(mat, k+1, j)+ mat[i-1] * mat[k] * mat[j])     
         if count < minimum_computations:    
             minimum_computations = count   
         return minimum_computations  
 
 matrix_sizes = [20, 30, 45, 50]  
-print("Minimum multiplications are", MatrixChain(matrix_sizes , 1, len(matrix_sizes)-1))  
+print("Minimum multiplications are", matrix_chain(matrix_sizes , 1, len(matrix_sizes)-1))  

Chapter04/CircularList.py

@@ -28,17 +28,26 @@ def append(self, data):
     def delete(self, data):
         current = self.head
         prev = self.head
+        flag = False
         while prev == current or prev != self.tail:
             if current.data == data:
                 if current == self.head:
+                    #item to be deleted is head node 
                     self.head = current.next
                     self.tail.next = self.head
+                elif current == self.tail:   
+                    #item to be deleted is tail node 
+                    self.tail = prev 
+                    prev.next = self.head 
                 else:
+                    #item to be deleted is an intermediate node 
                     prev.next = current.next
                 self.size -= 1
                 return
             prev = current
             current = current.next
+        if flag is False:
+            print("Item not present in the list")
 
 
     def iter(self):
@@ -93,11 +102,3 @@ def iter(self):
     counter += 1
     if counter > 2:
         break
-        
-        
-        
-        
-        
-        
-        
-

Chapter04/append_at_any_location_singly_linkedlist.py

@@ -7,6 +7,7 @@ def __init__(self, data=None):
 
 class SinglyLinkedList:
     def __init__ (self):
+        self.tail = None
         self.head = None
         self.size = 0
 

Chapter04/delete_operation_singly_linkedlist.py

@@ -6,16 +6,16 @@ def __init__(self, data=None):
 
 class SinglyLinkedList:
     def __init__ (self):
-        self.tail = None
+        self.head = None
         self.size = 0
 
     def append(self, data):
         # Encapsulate the data in a Node 
         node = Node(data)
-        if self.tail is None:
-            self.tail = node    
+        if self.head is None:
+            self.head = node    
         else: 
-            current = self.tail 
+            current = self.head 
             while current.next:
                 current = current.next 
             current.next = node
@@ -29,8 +29,8 @@ def delete_first_node (self):
 
 
     def delete_last_node (self): 
-        current = self.tail 
-        prev = self.tail 
+        current = self.head 
+        prev = self.head
         while current:
             if current.next is None:
                 prev.next = current.next 
@@ -40,12 +40,12 @@ def delete_last_node (self):
 
 
     def delete(self, data): 
-        current = self.tail 
-        prev = self.tail 
+        current = self.head 
+        prev = self.head 
         while current:
             if current.data == data:
-                if current == self.tail:
-                    self.tail = current.next 
+                if current == self.head:
+                    self.head = current.next 
                 else:
                     prev.next = current.next 
                 self.size -= 1
@@ -59,18 +59,26 @@ def delete(self, data):
 words.append('ham')
 words.append('spam')
 
+words.delete_first_node()
 
+current = words.head
+while current:
+    print(current.data)
+    current = current.next
+
+
+    
 words.delete_last_node()
 
-current = words.tail
+current = words.head
 while current:
     print(current.data)
     current = current.next
 
 
 
 words.delete('ham')
-current = words.tail
+current = words.head
 while current:
     print(current.data)
     current = current.next

Chapter04/doubly_linked_list.py

@@ -1,17 +1,17 @@
-class Node(object):
+class Node:
     def __init__ (self, data = None, next = None, prev = None):
         self.data = data 
         self.next = next
         self.prev = prev
 
-class DoublyLinkedList(object):
+class DoublyLinkedList:
     def __init__ (self):
         self.head = None
         self.tail = None
         self.count = 0
 
     def append(self, data):
-        #Append an item to the list.   
+        #Append an item at the end of the list.   
         new_node = Node(data, None, None)
         if self.head is None:
             self.head = new_node
@@ -49,21 +49,68 @@ def append_at_a_location(self, data):
             prev = current
             current = current.next            
 
+    def iter(self):
+        current = self.head 
+        while current:
+            val = current.data 
+            current = current.next 
+            yield val
+            
+
+    def contains(self, data):  
+        for node_data in self.iter():  
+            if data == node_data:  
+                print(" Data item is present in the list. ") 
+                return    
+        print(" Data item is not present in the list. ") 
+        return   
+
+
 
 
 words = DoublyLinkedList()
 words.append('egg')
 words.append('ham')
 words.append('spam')
 
+print("Items in doubly linked list before append")
 current = words.head
 while current:
     print(current.data)
     current = current.next
 
+words.append_at_start('book')
+
+print("Items in doubly linked list after append")
+current = words.head
+while current:
+    print(current.data)
+    current = current.next
+
+
+words.append('book')
+
+print("Items in doubly linked list after adding element at end.")
+current = words.head
+while current:
+    print(current.data)
+    current = current.next
 
+
+
 words.append_at_a_location('ham')
+print("Doubly linked list after adding an element after word \"ham\" in the list.")
 current = words.head
 while current:
     print(current.data)
     current = current.next
+
+
+words = DoublyLinkedList()  
+words.append('egg')  
+words.append('ham')  
+words.append('spam') 
+
+
+words.contains("ham")  
+words.contains("ham2") 

Chapter05/List_based_queue.py

@@ -23,12 +23,22 @@ def dequeue(self):
 
 
 
-q= ListQueue()
-q.enqueue(4)
-q.enqueue('dog')
-q.enqueue('cat')
-q.enqueue('monday')
+q = ListQueue()
+q.enqueue(20)
+q.enqueue(30)
+q.enqueue(40)
+q.enqueue(50)
+print(q.items)
+#Queue is full
+#[20, 30, 40]
 
 
-a= q.size1()
+data = q.dequeue()
+print(data)
+print(q.items)
+#20
+#[30, 40]
+
+
+a = q.size1()
 print(a)

Chapter05/Stack.py

@@ -43,11 +43,10 @@ def peek(self):
 
 
 
-words = stack()
-words.push('4')
-words.push('5')
-words.push('6')
-words.push('7')
+words = Stack()
+words.push('egg')
+words.push('ham')
+words.push('spam')
 
 #print the stack elements.
 current = words.top