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Stacks and queues
Basic operations
Implementation of stacks and queues
Stack and Queue in java.util
Data Structures and Algorithms in Java, Third Edition
Ch04–1
Stack operations
push(el)
put the element el on the top of the
stack;
pop()
take the topmost element from the
stack;
topEl()
return the topmost element in the stack
without removing it;
clear()
clear the stack;
isEmpty() check to see if the stack is empty;
Data Structures and Algorithms in Java, Third Edition
Ch04–2
Series of operations on a stack
push 5 push 9 push 4
5
9
5
pop topEl push 2
4
9
5
Data Structures and Algorithms in Java, Third Edition
9
5
9
5
Ch04–3
Applications of stacks
• delimiter matching
• operations on long integers
• history of visited pages through a Web browser
• undo sequence in a word processor
• sequence of method/function calls
Data Structures and Algorithms in Java, Third Edition
Ch04–4
Queue
enqueue(el) put the element el at the end of the queue;
dequeue() take the first element from the queue;
firstEl()
return the first element in the queue
without removing it;
clear()
clear the queue;
isEmpty() check to see if the queue is empty;
Data Structures and Algorithms in Java, Third Edition
Ch04–5
Series of operations on a queue
enqueue 5
dequeue
firstEl
5
enqueue 9
59
enqueue 7
597
97
97
Data Structures and Algorithms in Java, Third Edition
enqueue 2
Ch04–6
Applications of queues
• waiting lines in simulation problems
• scheduling processes by the operating system
• access to shared resources
Data Structures and Algorithms in Java, Third Edition
Ch04–7
Stack vs. queue
dequeue
enqueue
pop
push
stack – a LIFO structure (last in, first out)
queue – a FIFO structure (first in, first out)
Data Structures and Algorithms in Java, Third Edition
Ch04–8