day-184.cpp

/*
  Number of Recent Calls


You have a RecentCounter class which counts the number of recent requests within
a certain time frame.

Implement the RecentCounter class:

RecentCounter() Initializes the counter with zero recent requests.
int ping(int t) Adds a new request at time t, where t represents some time in
milliseconds, and returns the number of requests that has happened in the past
3000 milliseconds (including the new request). Specifically, return the number
of requests that have happened in the inclusive range [t - 3000, t]. It is
guaranteed that every call to ping uses a strictly larger value of t than the
previous call.



Example 1:

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

Explanation
RecentCounter recentCounter = new RecentCounter();
recentCounter.ping(1);     // requests = [1], range is [-2999,1], return 1
recentCounter.ping(100);   // requests = [1, 100], range is [-2900,100], return
2 recentCounter.ping(3001);  // requests = [1, 100, 3001], range is [1,3001],
return 3 recentCounter.ping(3002);  // requests = [1, 100, 3001, 3002], range is
[2,3002], return 3


Constraints:

1 <= t <= 104
Each test case will call ping with strictly increasing values of t.
At most 104 calls will be made to ping
*/

// Simple for loop O(N) time solution

class RecentCounter {
   public:
    vector<int> storeCounter;
    RecentCounter() { storeCounter = vector<int>(); }

    int ping(int t) {
        int low = t - 3000;
        int high = t;
        if (low < 1) low = 1;

        storeCounter.push_back(high);
        int N = storeCounter.size();
        int answer = 0;

        for (int idx = 0; idx <= N; idx++) {
            if (storeCounter[idx] >= low) return (N - idx);
        }

        return 0;
    }
};