算法（Algorithms）第4版 练习 1.3.8

//1.3.8
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 ResizingArrayStack<Item> implements Iterable<Item> {

private Item[] content;
private int number;

public ResizingArrayStack() {
content = (Item[]) new Object[1];
number = 0;
}

private void resizeArray(int max) {

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

Item[] temp = (Item[]) new Object[max];
for(int i = 0; i < number; i++) {
temp[i] = content[i];
}
content = temp;
}

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

public int size() {
return number;
}

public void push(Item item) {

if(number == content.length)
resizeArray(2 * content.length);

content[number++] = item;
}

public Item pop() {

if(isEmpty())
throw new NoSuchElementException("Stack is empty");

Item item = content[--number];
content[number] = null;//Aoid loitering

if(number == content.length/4 && number > 0)
resizeArray(content.length/2);

return item;
}

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

private class ReverseArrayIterator implements Iterator<Item> {

private int i = number;

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

@Override
public Item next() {
if(!hasNext())
throw new NoSuchElementException("Stack is empty");
return content[--i];
}

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

}

//Just for test(main)
private int arrayLength() {
return content.length;
}

public static void main(String[] args) {

ResizingArrayStack<String> stack = new ResizingArrayStack<String>();
StdOut.println("Initialized size:" + stack.size() + " Array Size:" + stack.arrayLength());

while (!StdIn.isEmpty()) {

String item = StdIn.readString();

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

stack.push(item);
StdOut.println("push success:" + item + " size:" + stack.size() + " Array Size:" + stack.arrayLength());

StdOut.print("Left on stack: ");
for (String s : stack) {
StdOut.print(s + " ");
}
StdOut.println();

} else {
if(stack.isEmpty())
StdOut.println("pop error, stack empty");
else {
StdOut.println("pop success:" + stack.pop() + " size:" + stack.size() + " Array Size:" + stack.arrayLength());

StdOut.print("Left on stack: ");
for (String s : stack) {
StdOut.print(s + " ");
}
StdOut.println();
}
}

}

}

}

Initialized size:0 Array Size:1
it
push success:it size:1 Array Size:1
Left on stack: it
was
push success:was size:2 Array Size:2
Left on stack: was it
-
pop success:was size:1 Array Size:2
Left on stack: it
the
push success:the size:2 Array Size:2
Left on stack: the it
best
push success:best size:3 Array Size:4
Left on stack: best the it
-
pop success:best size:2 Array Size:4
Left on stack: the it
of
push success:of size:3 Array Size:4
Left on stack: of the it
times
push success:times size:4 Array Size:4
Left on stack: times of the it
-
pop success:times size:3 Array Size:4
Left on stack: of the it
-
pop success:of size:2 Array Size:4
Left on stack: the it
-
pop success:the size:1 Array Size:2
Left on stack: it
it
push success:it size:2 Array Size:2
Left on stack: it it
was
push success:was size:3 Array Size:4
Left on stack: was it it
-
pop success:was size:2 Array Size:4
Left on stack: it it
the
push success:the size:3 Array Size:4
Left on stack: the it it
-
pop success:the size:2 Array Size:4
Left on stack: it it
-
pop success:it size:1 Array Size:2
Left on stack: it