<![CDATA[
CSE143 Stack/Queue Examples handout #8
Stack/Queue Methods
-------------------
For Stack<E>, we are using the Stack<E> implementation and we are using the
following operations:
public void push(E value); // push given value onto top of the stack
public E pop(); // removes and returns the top of the stack
public boolean isEmpty(); // returns whether or not stack is empty
public int size(); // returns number of elements in the stack
For Queue<E>, we are using the LinkedList<E> implementation and we are using
the following operations:
public void add(E value); // inserts given value at the end of the queue
public E remove(); // removes and returns the front of the queue
public boolean isEmpty(); // returns whether or not queue is empty
public int size(); // returns number of elements in the queue
Sample Program StackQueue.java
------------------------------
// Program that demonstrates some simple stack/queue operations
import java.util.*;
public class StackQueue {
public static void main(String[] args) {
Queue<Integer> q = makeRandomQueue(10);
System.out.println("initial queue = " + q);
System.out.println("sum = " + sum(q));
System.out.println("after sum queue = " + q);
System.out.println();
Stack<Integer> s = new Stack<Integer>();
queueToStack(q, s);
System.out.println("after queueToStack:");
System.out.println(" queue = " + q);
System.out.println(" stack = " + s);
System.out.println();
s = makeRandomStack(10);
System.out.println("initial stack = " + s);
System.out.println("sum = " + sum(s));
System.out.println("after sum stack = " + s);
System.out.println();
stackToQueue(s, q);
System.out.println("after stackToQueue:");
System.out.println(" stack = " + s);
System.out.println(" queue = " + q);
}
// pre : size >= 0
// post: returns a queue of size random values from 0 to 99
public static Queue<Integer> makeRandomQueue(int size) {
Random r = new Random();
Queue<Integer> q = new LinkedList<Integer>();
for (int i = 0; i < size; i++)
q.add(r.nextInt(100));
return q;
}
// pre : size >= 0
// post: returns a stack of size random values from 0 to 99
public static Stack<Integer> makeRandomStack(int size) {
Random r = new Random();
Stack<Integer> s = new Stack<Integer>();
for (int i = 0; i < size; i++)
s.push(r.nextInt(100));
return s;
}
// post: Values from q moved to s (added in queue order, front to back);
// q is empty
public static void queueToStack(Queue<Integer> q, Stack<Integer> s) {
while (!q.isEmpty()) {
int n = q.remove();
s.push(n);
}
}
// post: Values from s moved to q (added in stack order, top to bottom);
// s is empty
public static void stackToQueue(Stack<Integer> s, Queue<Integer> q) {
while (!s.isEmpty()) {
int n = s.pop();
q.add(n);
}
}
// post: Values from s moved to q (added in stack order, top to bottom);
// s is empty
// post: returns the sum of the values in q
public static int sum(Queue<Integer> q) {
int sum = 0;
for (int i = 0; i < q.size(); i++) {
int n = q.remove();
sum += n;
q.add(n);
}
return sum;
}
// post: returns the sum of the values in s
public static int sum(Stack<Integer> s) {
int sum = 0;
Queue<Integer> q = new LinkedList<Integer>();
while (!s.isEmpty()) {
int n = s.pop();
sum += n;
q.add(n);
}
queueToStack(q, s);
stackToQueue(s, q);
queueToStack(q, s);
return sum;
}
}
]]>