CMSC 341

1
CMSC 341

• Stacks and Queues

2
Stack ADT

• Restricted List
• only add to top
• only remove from top
• Examples
• pile of trays
• partial results
• local state

3
Relation to Previous List

• Using inheritance
• Stack Is-A List
• Need to pay special intention that List
  operations are
• properly performed
• Using aggregation
• Stack Has-A List

4
Stack.H

• include LinkedList.H
• template ltclass Objectgt
• class Stack
• public
• Stack()
• Stack(const Stack coll)
• Stack()
• bool isEmpty() const
• bool isFull() const
• const Object top() const
• void makeEmpty()
• void pop()
• void push(const Object x)
• Object topAndPop()
• const Stack operator(const Stack stk)

5
Stack.H (cont)

• protected
• const ListltObjectgt getList() const
• void setList(ListltObjectgt lst)
• ListItrltObjectgt getZeroth()
• private
• ListltObjectgt _theList
• ListItrltObjectgt _zeroth

6
Stack.C

• template ltclass Objectgt
• StackltObjectgtStack()
• _zeroth getList().zeroth()
• template ltclass Objectgt
• StackltObjectgtStack(const Stack stk)
• _theList stk.getList()
• _zeroth getList().zeroth()
• template ltclass Objectgt
• StackltObjectgtStack()
• template ltclass Objectgt
• bool StackltObjectgtisEmpty() const
• return getList().isEmpty()

7
Stack.C (cont)

• template ltclass Objectgt
• bool StackltObjectgtisFull()const
• return false
• template ltclass Objectgt
• const Object StackltObjectgttop() const
• if (isEmpty())
• throw StackException(top on empty stack)
• return getList().first().retrieve()
• template ltclass Objectgt
• void StackltObjectgtmakeEmpty ()
• getList().makeEmpty()

8
Stack.C (cont)

• template ltclass Objectgt
• void StackltObjectgtpop()
• if (isEmpty())
• throw StackException(pop on empty stack)
• getList().remove(top())
• template ltclass Objectgt
• void StackltObjectgtpush(const Object x)
• getList().insert(x, getZeroth())
• template ltclass Objectgt
• Object StackltObjectgttopAndPop ()
• if (isEmpty())
• throw StackException(topAndPop on empty
  stack)
• Object tmp top() pop()
• return tmp

9
Stack.C (cont)

• template ltclass Objectgt
• const StackltObjectgt StackltObjectgt
• operator(const Stack stk)
• if (this ! stk)
• setList(stk.getList())
• setZeroth(getList().zeroth())
• return this
• template ltclass Objectgt
• const ListltObjectgt StackltObjectgtgetList()
• return _theList
• template ltclass Objectgt
• ListItrltObjectgt StackltObjectgtgetZeroth ()
• return _zeroth

10
StackException.H

• class StackException
• public
• StackException() // Message is the empty
  string
• StackException(const string errorMsg)
• StackException(const StackException ce)
• StackException()
• const StackException
• operator(const StackException ce)
• const string errorMsg() const // Accessor for
  msg
• private
• string _msg

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StackException.C

• StackExceptionStackException()
• StackExceptionStackException(const string
  errorMsg)
• _msg errorMsg
• StackExceptionStackException(const
  StackException ce)
• _msg ce.errorMsg()
• StackExceptionStackException()

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StackException.C (cont)

• const StackException
• StackExceptionoperator(const StackException
  ce)
• if (this ce)
• return this // don't assign to itself
• _msg ce.errorMsg()
• return this
• const string StackExceptionerrorMsg() const
• return _msg

13
TestStack.C

• int main ()
• Stackltintgt stk
• stk.push(1)
• stk.push(2)
• printStack(stk)
• Stackltintgt otherstk
• otherstk stk
• printStack(otherstk)
• cout ltlt stk.topAndPop() ltlt endl
• cout ltlt stk.topAndPop() ltlt endl

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TestStack.C (cont)

• printStack(stk)
• printStack(otherstk)
• try
• stk.pop()
• catch (StackException e)
• cout ltlt e.errorMsg() ltlt endl

15
TestStack_aux.C

• template ltclass Objectgt
• void printStack( StackltObjectgt theStack )
• StackltObjectgt tmp
• if( theStack.isEmpty( ) )
• cout ltlt "Empty stack" ltlt endl
• return
• while (theStack.isEmpty() false)
• Object topObj theStack.top()
• cout ltlt topObj
• tmp.push(topObj) // save on other stack
• theStack.pop()
• if (theStack.isEmpty() false)
• cout ltlt ", "
• cout ltlt endl

16
TestStack_aux.C

• while (tmp.isEmpty() false)
• Object topObj tmp.top()
• theStack.push(topObj)
• tmp.pop()

17
Queue ADT

• Restricted List
• only add to end
• only remove from front
• Examples
• line waiting for service
• jobs waiting to print

18
Queue.H

• template ltclass Objectgt
• class Queue
• public
• explicit Queue(int capacity10)
• bool isEmpty() const
• bool isFull() const
• const Object getFront() const
• void makeEmpty()Object dequeue()void enqueue
  (const Object x)
• private
• vectorltObjectgt theArray
• int currentSize
• int front
• int back
• void increment (int x)

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Queue.C

• template ltclass Objectgt
• QueueltObjectgtQueue( int capacity ) theArray(
  capacity )
• makeEmpty( )
• template ltclass Objectgt
• void QueueltObjectgtmakeEmpty( )
• currentSize 0
• front 0
• back -1

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Queue.C (contd)

• template ltclass Objectgt
• void QueueltObjectgtenqueue(const Object x)
• if (isFull())
• throw Overflow()
• increment (back)
• theArrayback x
• currentSize
• template ltclass Objectgt
• void QueueltObjectgtincrement(int x)
• if (x theArray.size())
• x 0

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Queue.C (cont)

• template ltclass Objectgt
• Object QueueltObjectgtdequeue()
• if (isEmpty())
• throw Underflow()
• currentSize--
• Object frontItem theArrayfront
• increment(front)
• return frontItem

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theArray
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The Double-Ended Queue ADT

• The double ended queue is referred to as a Deque
  (rhymes with check)
• Restricted List
• add to the end
• remove from the end
• add to the front
• remove from the front
• Stacks and Queues are often implemented using a
  deque