leetcode讲解--933. Number of Recent Calls

题目

Write a class RecentCounter to count recent requests.

It has only one method: ping(int t), where t represents some time in milliseconds.

Return the number of pings that have been made from 3000 milliseconds ago until now.

Any ping with time in [t - 3000, t] will count, including the current ping.

It is guaranteed that every call to ping uses a strictly larger value of t than before.

Example 1:

Input: inputs = ["RecentCounter","ping","ping","ping","ping"], inputs = [[],[1],[100],[3001],[3002]]
Output: [null,1,2,3,3]

Note:

1. Each test case will have at most 10000 calls to ping.
2. Each test case will call ping with strictly increasing values of t.
3. Each call to ping will have 1 <= t <= 10^9.

题目地址

讲解

这道题最重要的是看懂题，每个ping都附带一个时间点，求这个时间点往前3000毫秒内的ping数量。这里我使用了一个队列来实现。

Java代码

class RecentCounter {
    
    private Queue<Integer> queue;

    public RecentCounter() {
        queue = new LinkedList<>();
    }
    
    public int ping(int t) {
        while(queue.size()>0 && queue.peek()<t-3000){
            queue.poll();
        }
        queue.offer(t);
        return queue.size();
    }
}

/**
 * Your RecentCounter object will be instantiated and called as such:
 * RecentCounter obj = new RecentCounter();
 * int param_1 = obj.ping(t);
 */