java 队列和栈相互实现
2024-09-01 08:03:23
一、队列实现栈
public class queue2stack {
public static void main(String[] args) {
QS qs = new QS();
qs.push("1");
qs.push("2");
qs.push("3");
System.out.println(qs.pop());
System.out.println(qs.pop());
System.out.println(qs.peek());
QS qs2 = new QS();
qs2.push("1");
qs2.push("2");
qs2.push("3");
System.out.println(qs2.pop());
System.out.println(qs2.pop());
System.out.println(qs2.peek());
}
static class QS{
private Queue queueMain = new ArrayDeque();
private Queue queueWork = new ArrayDeque();
public boolean push(Object object){
try {
queueMain.offer(object);
return true;
} catch (Exception e) {
return false;
}
}
public int size() {
return queueMain.size();
}
public Object pop(){
if(queueMain.isEmpty()) {
return null;
}
Queue temp = new ArrayDeque();
int size = queueMain.size();
for (int i = 0; i < size - 1; i ++) {
temp.offer(queueMain.poll());
}
Object o = queueMain.poll();
int size1 = temp.size();
for (int i = 0; i < size1; i ++) {
queueMain.offer(temp.poll());
}
return o;
}
public Object peek(){
if(queueMain.isEmpty()) {
return null;
}
Queue temp = new ArrayDeque();
int size = queueMain.size();
for (int i = 0; i < size - 1; i ++) {
temp.offer(queueMain.poll());
}
Object o = queueMain.peek();
temp.offer(queueMain.poll());
int size1 = temp.size();
for (int i = 0; i < size1; i ++) {
queueMain.offer(temp.poll());
}
return o;
}
public boolean empty(){
return queueMain.isEmpty();
}
/**********优化***********/
public boolean push2(Object object){
try {
if (queueMain.isEmpty() && queueWork.isEmpty()) {
queueMain.offer(object);
}
if (queueMain.isEmpty()) {
queueWork.offer(object);
}
if(queueWork.isEmpty()) {
queueMain.offer(object);
}
return true;
} catch (Exception e) {
return false;
}
}
public Object pop2(){
if(queueMain.isEmpty() && queueWork.isEmpty()) {
return null;
}
if (queueMain.isEmpty()) {
while (queueWork.size() > 1) {
queueMain.offer(queueWork.poll());
}
return queueWork.poll();
}
if (queueWork.isEmpty()) {
while (queueMain.size() > 1) {
queueWork.offer(queueMain.poll());
}
return queueMain.poll();
}
return null;
}
public Object peek2(){
if(queueMain.isEmpty() && queueWork.isEmpty()) {
return null;
}
if (queueMain.isEmpty()) {
while(queueWork.size() > 1) {
queueMain.offer(queueWork.poll());
}
Object e = queueWork.peek();
queueMain.offer(queueWork.poll());
return e;
}
if (queueWork.isEmpty()) {
while(queueMain.size() > 1) {
queueWork.offer(queueMain.poll());
}
Object e = queueMain.peek();
queueWork.offer(queueMain.poll());
return e;
}
return null;
}
}
}
二、栈实现队列
public class Stack2queue {
public static void main(String[] args) {
SQ sq = new SQ();
sq.offer("a");
sq.offer("b");
sq.offer("c");
System.out.println(sq.poll());
System.out.println(sq.poll());
sq.offer("d");
sq.offer("e");
System.out.println(sq.poll());
System.out.println(sq.peek());
System.out.println(sq.poll());
System.out.println(sq.poll());
}
static class SQ{
private Stack stackMain = new Stack();
private Stack stackWork = new Stack();
public boolean offer(Object ele) {
stackMain.push(ele);
return true;
}
public Object poll() {
if (stackWork.empty()) {
while(stackMain.size() > 0) {
stackWork.push(stackMain.pop());
}
}
if (stackWork.empty()) {
return null;
}
return stackWork.pop();
}
public Object peek() {
if (stackWork.empty()) {
while(stackMain.size() > 0) {
stackWork.push(stackMain.pop());
}
}
if (stackWork.empty()) {
return null;
}
return stackWork.peek();
}
}
}
结果自行运行测试
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