算法（Algorithms）第4版 练习 1.3.14

//1.3.14
package com.qiusongde;

import java.util.Iterator;
import java.util.NoSuchElementException;

import edu.princeton.cs.algs4.StdIn;
import edu.princeton.cs.algs4.StdOut;

public class ResizingArrayQueue<Item> implements Iterable<Item> {

private Item[] content;
private int head;
private int tail;
private int n;

public ResizingArrayQueue() {
content = (Item[])new Object[1];
n = head = tail = 0;
}

public int size() {
return n;
}

public boolean isEmpty() {
return n == 0;
}

private void resizeArray(int max) {

if(max < n)
throw new IllegalArgumentException("the size of new array must larger than the size of Queue");

Item[] temp = (Item[]) new Object[max];

for(int i = 0; i < n; i++) {
temp[i] = content[(head + i) % content.length];
}
head = 0;
tail = n;
content = temp;
}

public void enqueue(Item item) {

if(n == content.length) {//full
resizeArray(content.length * 2);//double array
}

content[tail++] = item;
if(tail == content.length) {
tail = 0;//wrap around
}
n++;

}

public Item dequeue() {

if(isEmpty()) {//empty
throw new NoSuchElementException("Queue is empty");
}

Item item = content[head];
content[head] = null;//avoid loitering
head++;//next
if(head == content.length) {
head = 0;//wrap around
}
n--;

if(n == content.length/4 && n > 0) {
resizeArray(content.length/2);
}

return item;
}

@Override
public String toString() {
String s;

s = "Size:" + n +  " ArrayLength:" + content.length + " head:" + head + " tail:" + tail +"\n";
for(Item item : content) {
s += item + " ";
}
s += "\n";

return s;
}

@Override
public Iterator<Item> iterator() {
return new ResizingArrayQueueIterator();
}

private class ResizingArrayQueueIterator implements Iterator<Item> {

private int number = n;//initialize
private int start = head;//initialize

@Override
public boolean hasNext() {
return number > 0;
}

@Override
public Item next() {

if(!hasNext())
throw new NoSuchElementException("Queue is empty");

Item item = content[start++];
if(start == content.length)
start = 0;//wrap around
number--;

return item;
}

@Override
public void remove() {
throw new UnsupportedOperationException();
}

}

public static void main(String[] args) {

ResizingArrayQueue<String> queue = new ResizingArrayQueue<String>();
StdOut.println(queue);

while (!StdIn.isEmpty()) {

String item = StdIn.readString();

if (!item.equals("-")) {

queue.enqueue(item);

StdOut.println("enqueue success:" + item);
StdOut.println(queue);

} else {
if(queue.isEmpty())
StdOut.println("dequeue error, stack empty");
else {

StdOut.println("dequeue success:" + queue.dequeue());
StdOut.println(queue);

}
}

}

StdOut.println("Left in the ResizingArrayQueue:");
for(String s : queue) {
StdOut.print(s + " ");
}
StdOut.println();

}

}

Size:0 ArrayLength:1 head:0 tail:0
null

to
enqueue success:to
Size:1 ArrayLength:1 head:0 tail:0
to

or
enqueue success:or
Size:2 ArrayLength:2 head:0 tail:0
to or

not
enqueue success:not
Size:3 ArrayLength:4 head:0 tail:3
to or not null

to
enqueue success:to
Size:4 ArrayLength:4 head:0 tail:0
to or not to

be
enqueue success:be
Size:5 ArrayLength:8 head:0 tail:5
to or not to be null null null

-
dequeue success:to
Size:4 ArrayLength:8 head:1 tail:5
null or not to be null null null

-
dequeue success:or
Size:3 ArrayLength:8 head:2 tail:5
null null not to be null null null

-
dequeue success:not
Size:2 ArrayLength:4 head:0 tail:2
to be null null

-
dequeue success:to
Size:1 ArrayLength:2 head:0 tail:1
be null

-
dequeue success:be
Size:0 ArrayLength:2 head:1 tail:1
null null

to
enqueue success:to
Size:1 ArrayLength:2 head:1 tail:0
null to

be
enqueue success:be
Size:2 ArrayLength:2 head:1 tail:1
be to

Left in the ResizingArrayQueue:
to be