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MaxQueue.java
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56 lines (48 loc) · 1.69 KB
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package Chap6;
import java.util.Deque;
import java.util.LinkedList;
/**
* 定义一个队列，实现max方法得到队列中的最大值。
* 要求入列、出列以及邱最大值的方法时间复杂度都是O(1)
*/
public class MaxQueue {
private Deque<Integer> maxDeque = new LinkedList<>();
private Deque<Integer> dataDeque = new LinkedList<>();
public void offer(int number) {
dataDeque.offerLast(number);
// 即将要存入的元素比当前队列最大值还大，存入该元素
if (maxDeque.isEmpty() || number > maxDeque.peekFirst()) maxDeque.offerFirst(number);
// 即将要存入的元素不超过当前队列最大值，再将最大值存入一次
else maxDeque.offerFirst(maxDeque.peekFirst());
}
public void poll() {
if (dataDeque.isEmpty()) throw new RuntimeException("队列已空");
dataDeque.pollFirst();
maxDeque.pollFirst();
}
public int max() {
if (maxDeque.isEmpty()) throw new RuntimeException("队列已空");
return maxDeque.peekFirst();
}
public static void main(String[] args) {
MaxQueue maxQueue = new MaxQueue();
maxQueue.offer(2);
maxQueue.offer(3);
maxQueue.offer(4);
maxQueue.offer(2);
maxQueue.offer(6);
maxQueue.offer(2);
maxQueue.offer(5);
maxQueue.offer(1);
System.out.println(maxQueue.max());
maxQueue.poll();
maxQueue.poll();
maxQueue.poll();
maxQueue.poll();
System.out.println(maxQueue.max());
maxQueue.poll();
System.out.println(maxQueue.max());
maxQueue.poll();
System.out.println(maxQueue.max());
}
}