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Chapter 15, Problem 12PP
Program Plan Intro

Priority Queue

Program Plan:

queue.h:

  • Include required header files.
  • Create a namespace named “queuesavitch”.
    • Create a structure.
      • Declare a variable and a pointer.
    • Declare a class “Queue”.
      • Inside “public” access specifier.
        • Declare the constructor and destructor.
        • Declare the functions “add ()”, “remove ()”, “empty ()”.
      • Inside the “protected” access specifier,
        • Create a pointer “front” that points to the head of the linked list.
        • Create a pointer “back” that points to the other end of the linked list.

queue.cpp:

  • Include required header files.
  • Create a namespace named “queuesavitch”.
    • Declare the constructor.
    • Inside the parameterized constructor,
      • Declare the temporary point that moves through the nodes from front to the back.
      • Create a pointer “temp_ptr_new” that is used to create new nodes.
      • Create new nodes.
      • Assign “emp_ptr_old->link” to “temp_ptr_old”.
      • Using while condition “temp_ptr_old != NULL”.
        • Create a new node.
        • Assign the temporary old data to the new pointer.
        • Assign NULL to the link of temporary new pointer.
        • Assign “temp_ptr_new” to “back->link”.
        • Assign “temp_ptr_new” to “back”.
        • Assign “temp_ptr_old->link” to “temp_ptr_old”.
    • Give definition for the destructor.
      • Declare a variable “next”.
      • Do till the queue is empty.
        • Remove the items using “remove ()” method.
    • Give definition for “empty ()” to check if the queue is empty or not.
      • Return “back == NULL”.
    • Give definition for the method “add ()”.
      • Check if the queue is empty.
        • Create a new node.
        • Assign the item to the data field.
        • Make the front node as null.
        • Assign front as the back.
      • Else,
        • Create a new pointer.
        • Create a new node.
        • Assign the item to “temp_ptr->data”.
        • Assign “NULL” to “temp_ptr->link”.
        • Assign temporary pointer to the link.
        • Assign temporary pointer to the back.
    • Give definition for the method “remove ()”.
      • Check if the queue is empty.
        • Print the message.
      • Store the value into the variable “result”.
      • Create an object “discard” for the pointer “QueueNodePtr”.
      • Assign “front” to “discard”.
      • Assign the link of front to “front”.
      • Check if the front is null.
        • Assign null to the back.
      • Delete the object “discard”.
      • Return “result”.

PriorityQueue.h:

  • Include required header files.
  • Create a namespace named “queuesavitch”.
    • Declare a class “PriorityQueue”.
      • Inside “public” access specifier,
        • Declare the constructor and destructor.
        • Declare the virtual function.

PriorityQueue.cpp:

  • Include required header files.
  • Create a namespace named “queuesavitch”.
    • Declare the constructor and destructor.
    • Give function to remove items.
      • Check if the queue is empty.
        • Print the messge.
      • Assing “front->data” to “smallest”.
      • Assign “NULL” to “nodeBeforeSmallest”.
      • Assign “front” to “previousPtr”.
      • Assign the link of front to “current”.
      • Using while condition “current != NULL”,
        • Check if the data is smaller.
          • Assing “current->data” to “smallest”.
          • Assign “previousPtr” to “nodeBeforeSmallest”.
        • Assign “current” to “previousPtr”.
        • Assign “current->link” to “current”.
      • Create an object “discard”.
      • Check if the node is null.
        • Assign “front” to “discard”.
        • Assign the link of front to “front”.
      • Check if the link is equal to back.
        • Assign “back” to “discard”.
        • Assign “nodeBeforeSmallest” to “back”.
        • Assign “NULL” to “back->link”.
      • Else,
        • Assign “nodeBeforeSmallest->link” to “discard”.
        • Assign “discard->link” to “nodeBeforeSmallest->link”.
      • Check if front is equal to null.
        • Assign “NULL” to “back”.
      • Delete the object “discard”.
      • Return the smallest item.

main.cpp:

  • Include required header files.
  • Inside the “main ()” function,
    • Create an object for “PriorityQueue”.
    • Add the integers to the queue using “add ()” method.
    • While “(!que.empty())”,
      • Call the function “que.remove()”.
    • Declare a character variable.
    • Get a character.
    • Return the statement.

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Chapter 15 Solutions

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