ADT Stack Operations and Examples

2. Create an empty stack. Determine whether a stack is empty. Add a new item to the stack. Remove from the stack the item that was added most recently. Remove all the items from the stack. Retrieve from the stack the item that was added most recently. ADT Stack Operations

3. Figure 6.1 Stack of cafeteria dishes

4. LIFO (Last-In, First-Out) - Stack FIFO (First-In, First-Out) - Queue ADT Stack Operations

5. createStack() // Creates an empty stack isEmpty() // Determines whether a stack is empty push(newItem) throws StackException // Adds newItem to the top of the stacks. Throws StackException if failed. pop() throws StackException // Retrieves and then removes the top of the stack. Throws StackException if not successful. popAll() // Removes all items from the stack peek() throws StackException //Retrieves the top of the stack. Retrieval does not change the stack. Throws Stack Exception if failed. Pseudocode for the ADT Stack Operations

6. displayBackward(stack) // Displays the input line in reversed order by writing the contents of stack // Writing the contents of stack. stack = readAndCorrect() while (!stack.isEmpty()) { newChar = stack.pop() Write newChar } // end while Advance to new line Using the ADT stack in a solution

7. readAndCorrect() // Reads the input line and returns the corrected version as a stack. // For each character read, either enters it into the stack or, if it is // ‘<-’, corrects the contents of stack stack.createStack() Read newChar while (newChar is not the end-of-line symbol) { if (newChar is not ‘<-’) { stack.push(newChar) } else if (!stack.isEmpty()) { oldChar = stack.pop() } // end if Read newChar } // end while return stack Using the ADT stack in a solution

8. Checking for Balanced Braces Simple Applications of the ADT Stack

9. Figure 6.2 Traces of the algorithm that checks for balanced braces

10. Array-based Implementation Reference-based Implementation Comparing Implementations Implementations of the ADT Stack

11. Figure 6.3 Implementation of the ADT stack that use a) an array; b) a linked list; c) an ADT list

12. Figure 6.4 An array-based implementation

13. Figure 6.5 A reference-based implementation

14. Figure 6.6 An implementation that uses the ADT list

15. Figure 6.7 The action of a postfix calculator when evaluating the expression 2 * (3 + 4)

16. Figure 6.8 A trace of the algorithm that converts the infix expression a - (b + c * d)/e to postfix form

17. Figure 6.9 Flight map for HPAir

18. Figure 6.10 The stack of cities as you travel a) from P; b) to R; c) to X; d) back to R; e) back to P; f) to W

19. Figure 6.11 The stack of cities a) allowing revisits and b) after backtracking when revisits are not allowed

20. Figure 6.12 A trace of the search algorithm, given the flight map in Figure 6-9

21. Figure 6.13 A piece of a flight map

22. Figure 6.14 Visiting city P, then R, then X: a) box trace versus b) stack

23. Figure 6.15 Backtracking from city X, then R, then P: a) box trace versus b) stack

24. Figure 6.16 Flight map for Self-Test Exercise 9 and Exercise 11

25. Figure 6.17 Railroad switching system for Exercise 2

26. Figure 6.18 Adjacency list for the flight map in Figure 6-9