# leetcode\_933

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:

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

## Solutions

1. **deque**

```cpp
class RecentCounter {
public:
    deque<int> times;
    RecentCounter() {

    }

    int ping(int t) {
        while (times.size() && times.front() < t - 3000)
            times.pop_front();
        times.push_back(t);
        return times.size();
    }
};

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