Number of Recent Calls in Python

Suppose we want to write a class called RecentCounter to count recent requests. This class has only one method: ping(t), where t is representing some time in milliseconds. This will 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. And it is guaranteed that every call to ping uses a strictly larger value of t than before.

So, if the input is like Call ping four times ping(1), ping(100), ping(3001), ping(3002), then the output will be 1,2,3,3 respectively.

To solve this, we will follow these steps −

• Initialize the class by making one queue, initially this is empty
• Define a function ping(). This will take t
• while size of queue is not 0 and t - queue[0] > 3000, do
  • delete first element from queue
• insert t at the end of queue
• return size of queue

Let us see the following implementation to get better understanding −

Example

 Live Demo

class RecentCounter:
   def __init__(self):
      self.queue = []
   def ping(self, t):
      while len(self.queue) and t - self.queue[0] > 3000:
         self.queue.pop(0)
         self.queue.append(t)
      return len(self.queue)
ob = RecentCounter()
print(ob.ping(1))
print(ob.ping(100))
print(ob.ping(3001))
print(ob.ping(3002))

Input

ob.ping(1) ob.ping(100) ob.ping(3001) ob.ping(3002)

Output

1
2
3
3

Arnab Chakraborty

Updated on: 04-Jul-2020

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