嘿伙计们，我在尝试打印循环队列数组时遇到问题 这是我的代码:
public class CircularQueue {
private int [] queue;
private int front, rear;
// do not change the constructor
CircularQueue() {
queue = new int [5];
front = 0;
rear = -1;
}
// FILL IN:
// throws DSException if out of space
public void enqueue ( int item ) throws DSException {
if ( front == 0 && rear == -1 ){
throw new DSException();
}
queue[rear+1] = item;
rear = (rear+1)%queue.length;
}
// FILL IN:
// throws DSException if no element in the queue
// return the dequeued value
public int dequeue () throws DSException {
if ( front == 0 && rear == -1 ){
throw new DSException();
}
int temp = queue[front];
queue[front] = 0;
front = (front+1)%queue.length;
return temp;
}
// FILL IN:
// return the value at beginning of the queue
// throws DSException if no element in the queue
public int first () throws DSException {
return front;
}
// FILL IN:
// print the circular queue in the following format
// - print "+" before the value at the front
// - print "-" after the value at the rear
// - print "." for the places without valid element.
public void print () {
System.out.print(" <");
for ( int i = 0; i < queue.length; i++ ){
if ( front == 0 && rear == -1 ){
System.out.print("."+"\t");
} else if ( i == front ) {
System.out.print("+"+ queue[i]);
} else if ( i == rear ) {
System.out.print( queue[i]+ "-");
} else if ( i == front && i == rear) {
System.out.print("+"+ queue[i] +"-");
} else {
System.out.print( queue[i] );
}
}
System.out.print(">\n");
}
}
这是结果 空的: <。 。 。 。 。 > 入队(0):
我应该将 0-4 入队并出队一些元素，但它在入队 0 后停止。
最佳答案
循环队列可以处于 3 种状态，其不变量如下:
空 : 前 == -1 && 后 == -1
满:(后+1)%queue.length ==前
非空非满:不满足上述条件
<br/>
public class CircularQueue {
<pre><code>private int [] queue;
private int front, rear;
// do not change the constructor
CircularQueue() {
queue = new int [5];
front = -1;
rear = -1;
}
// FILL IN:
// throws DSException if out of space
public void enqueue ( int item ) throws DSException,Exception {
if ( front == -1 && rear == -1 ){
front = 0;
rear = 0;
queue[rear] = item;
}
else if((rear+1)%queue.length == front) {
throw new Exception("Full");
}
else {
rear = (rear+1)%queue.length;
queue[rear] = item;
}
}
// FILL IN:
// throws DSException if no element in the queue
// return the dequeued value
public int dequeue () throws DSException {
if ( front == -1 && rear == -1 ){
throw new DSException();
}
else {
int ret = queue[front];
if(rear==front) {
rear = -1;
front = -1;
}
else {
front = (front+1)%queue.length;
}
return ret;
}
}
// FILL IN:
// return the value at beginning of the queue
// throws DSException if no element in the queue
public int first () throws DSException {
if(front==-1 && rear ==-1) {
throw new DSException();
}
return queue[front];
}
// FILL IN:
// print the circular queue in the following format
// - print "+" before the value at the front
// - print "-" after the value at the rear
// - print "." for the places without valid element.
public void print () {
if(front==-1 && rear == -1) {
for(int i=0;i<queue.length;i++) {
System.out.print(".");
}
}
else {
if(front<=rear) {
for(int i=0;i<=front-1;i++) {
System.out.print(".");
}
System.out.print("+");
for(int i=front;i<=rear;i++) {
System.out.print(queue[i]);
}
System.out.print("-");
for(int i=rear+1;i<=queue.length-1;i++) {
System.out.print(".");
}
}
else {
for(int i=0;i<=rear;i++) {
System.out.print(queue[i]);
}
System.out.print("-");
for(int i=rear+1;i<=front-1;i++) {
System.out.print(".");
}
System.out.print("+");
for(int i=front;i<=queue.length-1;i++) {
System.out.print(queue[i]);
}
}
}
}
</code></pre>
<p>}</p>
关于java - 循环队列java打印不正确，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/15411419/