Problem URL: Number of recent calls

We will use a queue to store the recent calls. We will remove the calls that are not in the range of 3000ms. Then we will return the size of the queue.

class RecentCounter:
    def __init__(self):
        self.q = collections.deque()

    def ping(self, t: int) -> int:
        self.q.append(t)
        while self.q[0] < t-3000:
            self.q.popleft()
        return len(self.q)

# Your RecentCounter object will be instantiated and called as such:
# obj = RecentCounter()
# param_1 = obj.ping(t)

Time complexity: O(n)
Space complexity: O(n)