[英]Why isn't my dequeue method working for my treeMap PriceQueue?
I have a PriceQueue class and I have gotten all my tests to pass except 2. Thenones that fail are: 我有一个PriceQueue类,我已经通过了所有的测试,除了2.失败的Thenones是:
public void test05DeleteBackInOrder() {
PriceQueue pq = new PriceQueue();
pq.enqueue(p101);
pq.enqueue(p202);
pq.enqueue(p303);
pq.enqueue(p404);
pq.enqueue(p505);
assertTrue(pq.delete(p303));
assertTrue(pq.delete(p404));
assertTrue(pq.delete(p505));
assertEquals(p101, pq.dequeue());
assertEquals(p202, pq.dequeue());
pq = new PriceQueue();
pq.enqueue(p101);
pq.enqueue(p202);
pq.enqueue(p303);
pq.enqueue(p404);
pq.enqueue(p505);
assertTrue(pq.delete(p303));
assertTrue(pq.delete(p404));
assertTrue(pq.delete(p505));
pq.enqueue(p303);
pq.enqueue(p404);
assertEquals(p101, pq.dequeue());
assertEquals(p202, pq.dequeue());
assertEquals(p303, pq.dequeue()); //This is where it is failing
assertEquals(p404, pq.dequeue());
}
and 和
public void test05DeleteMiddleInOrder() {
PriceQueue pq = new PriceQueue();
pq.enqueue(p101);
pq.enqueue(p202);
pq.enqueue(p303);
pq.enqueue(p404);
pq.enqueue(p505);
assertTrue(pq.delete(p202));
assertTrue(pq.delete(p303));
assertTrue(pq.delete(p404));
assertEquals(p101, pq.dequeue());
assertEquals(p505, pq.dequeue()); // This is where it fails
pq = new PriceQueue();
pq.enqueue(p101);
pq.enqueue(p202);
pq.enqueue(p303);
pq.enqueue(p404);
pq.enqueue(p505);
assertTrue(pq.delete(p202));
assertTrue(pq.delete(p303));
assertTrue(pq.delete(p404));
pq.enqueue(p202);
pq.enqueue(p303);
assertEquals(p101, pq.dequeue());
assertEquals(p505, pq.dequeue());
assertEquals(p202, pq.dequeue());
assertEquals(p303, pq.dequeue());
}
These are the ones that are failing and I don't understand where it is that I am missing deleting the prie so that it dequeues correctly. 这些是失败的,我不明白我错过了删除prie以便它正确出列的地方。 Here is my code here:
这是我的代码:
public Price dequeue() {
if (isEmpty()) throw new NoSuchElementException("Queue underflow");
Price price = first.price;
first = first.next;
n--;
if (isEmpty()) last = null;
hold.remove(hold.lastKey());
// to avoid loitering
return price;
}
/**
* Deletes a Price from the queue if it was present.
* @param price the Price to be deleted.
* @return {@code true} if the Price was deleted and {@code false} otherwise
*/
public boolean delete(Price price) {
// TODO implelment me!!!
// Make sure the running time is no worse than logrithmic!!!
// You will want to use Java's TreeMap class to map Prices to the node
// that precedes the Price in the queue
//last node==special case
//^^ requires resetting prev. to null, and val to next
if (hold.containsKey(price)) {
Node temp = hold.get(price);
//if (price.equals(f))
if (price.equals(first.price) && n >= 3) {
first = first.next;
n--;
hold.remove(price);
return true;
}
if (price.equals(first.price)) {
first = first.next;
hold.remove(price);
n--;
return true;
}
if (price.equals(last.price)) {
temp.next = null;
last = temp;
n--;
hold.remove(price);
return true;
}
if (temp.next != (null)) {
temp.next = temp.next.next;
n--;
hold.remove(price);
return true;
}
return true;
}
else return false;
}
Any help is appreciated even if it is a tip or hint. 任何帮助即使是小费或暗示也会受到赞赏。 If anything else is needed please let me know and I will supply, these are just the parts of my code.
如果需要其他任何东西请告诉我,我会提供,这些只是我的代码的一部分。 Thank you!
谢谢!
A quick answer about standard de-queuing would be to simply return the output of remove. 关于标准出队的快速回答是简单地返回remove的输出。
public Price dequeue(){
return some_list.remove(0); //null if empty
}
Remove returns the element it removes, and automatically shifts the elements following the removed item 1 to the left. Remove返回它删除的元素,并自动将删除的项目1后面的元素移到左侧。 If the item does not exist (list is empty) then it will return null.
如果该项不存在(列表为空),则它将返回null。
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