Two stacks implement one queue and two queues implement one stack (Java), and two queues implement java

Two stacks implement one queue and two queues implement one stack (Java), and two queues implement java
Two stacks implement one queue

Import java. util. stack; public class Demo07 {Stack <Integer> stack1 = new Stack <Integer> (); Stack <Integer> stack2 = new Stack <Integer> (); public void push (int node) {stack1.push (node);} public int pop () {if (stack2.size () <= 0) {while (stack1.size ()> 0) {/* int data = stack1.peek (); // view the top element of the stack, but do not remove it stack1.pop (); // The top element stack2.push (data) is displayed ); // press */stack2.push (stack1.pop () ;}} if (stack2.isEmpty () {try {throw new Exception ("queue is empty. ");} catch (Exception e) {}}/*** int head = stack2.peek (); * stack2.pop (); */int head = stack2.pop (); return head ;}}

Two queues implement one stack

Import java. util. arrayDeque; import java. util. queue; public class Demo08 {Queue <Integer> queue1 = new ArrayDeque <> (); Queue <Integer> queue2 = new ArrayDeque <> (); public void push (int node) {// if both stacks are empty, queue1 if (queue1.isEmpty () & queue2.isEmpty () {queue1.add (node); return ;}// if queue1 is empty, queue2 has elements, which are directly put into queue2 if (queue1.isEmpty () {queue2.add (node); return;} if (queue2.isEmpty () {queue1.add (Node); return ;}} public int pop () {// when both stacks are empty, if (queue1.isEmpty () & queue2.isEmpty ()) {try {throw new Exception ("stack is empty");} catch (Exception e) {}}// if queue1 is empty, queue2 has elements, add the elements of queue2 to queue1 in sequence until the last element is displayed. If (queue1.isEmpty () {while (queue2.size ()> 1) {queue1.add (queue2.poll ();} return queue2.poll ();} if (queue2.isEmpty ()) {while (queue1.size ()> 1) {queue2.add (queue1.poll ();} return queue1.poll ();} return (Integer) null ;} public static void main (String [] args) {Demo08 demo08 = new Demo08 (); demo08.push (1); demo08.push (2); demo08.push (3); demo08.push (4 ); system. out. println (demo08.pop (); System. out. println (demo08.pop (); demo08.push (5); System. out. println (demo08.pop (); System. out. println (demo08.pop (); System. out. println (demo08.pop ());}}

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