_362_DesignHitCounter.java

package leetcode_1To300;

import java.util.LinkedList;
import java.util.Queue;

/**
 * 本代码来自 Cspiration，由 @Cspiration 提供
 * 题目来源：http://leetcode.com
 * - Cspiration 致力于在 CS 领域内帮助中国人找到工作，让更多海外国人受益
 * - 现有课程：Leetcode Java 版本视频讲解（1-900题）（上）（中）（下）三部
 * - 算法基础知识（上）（下）两部；题型技巧讲解（上）（下）两部
 * - 节省刷题时间，效率提高2-3倍，初学者轻松一天10题，入门者轻松一天20题
 * - 讲师：Edward Shi
 * - 官方网站：https://cspiration.com
 * - 版权所有，转发请注明出处
 */
public class _362_DesignHitCounter {
    /**
     * 362. Design Hit Counter
     * Design a hit counter which counts the number of hits received in the past 5 minutes.

     Each function accepts a timestamp parameter (in seconds granularity) and you may assume that calls are being made to the system in chronological order (ie, the timestamp is monotonically increasing). You may assume that the earliest timestamp starts at 1.

     It is possible that several hits arrive roughly at the same time.

     Example:
     HitCounter counter = new HitCounter();

     // hit at timestamp 1.
     counter.hit(1);

     // hit at timestamp 2.
     counter.hit(2);

     // hit at timestamp 3.
     counter.hit(3);

     // get hits at timestamp 4, should return 3.
     counter.getHits(4);

     // hit at timestamp 300.
     counter.hit(300);

     // get hits at timestamp 300, should return 4.
     counter.getHits(300);

     // get hits at timestamp 301, should return 3.
     counter.getHits(301);

     1, Queue
     2, 数组

     */

    Queue<Integer> queue;

    /** Initialize your data structure here. */
    public _362_DesignHitCounter() {
        queue = new LinkedList<>();
    }

    /** Record a hit.
     @param timestamp - The current timestamp (in seconds granularity). */
    public void hit(int timestamp) {
        queue.offer(timestamp);
    }

    /** Return the number of hits in the past 5 minutes.
     @param timestamp - The current timestamp (in seconds granularity). */
    public int getHits(int timestamp) {
        while (!queue.isEmpty() && timestamp - queue.peek() >= 300) {
            queue.poll();
        }
        return queue.size();
    }

    private int[] times;
    private int[] hits;

    public void DesignHitCounter2() {
        times = new int[300];
        hits = new int[300];
    }

    /** Record a hit.
     @param timestamp - The current timestamp (in seconds granularity). */
    public void hit2(int timestamp) {
        int index = timestamp % 300;
        if (times[index] != timestamp) {
            times[index] = timestamp;
            hits[index] = 1;
        } else {
            hits[index]++;
        }
    }

    /** Return the number of hits in the past 5 minutes.
     @param timestamp - The current timestamp (in seconds granularity). */
    public int getHits2(int timestamp) {
        int res = 0;
        for (int i = 0; i < 300; i++) {
            if (timestamp - times[i] < 300) {
                res += hits[i];
            }
        }
        return res;
    }
}