**Hit Counter - Amazon Top Interview Questions**

### Problem Statement :

Implement a hit counter which keeps track of number of the number of hits in the last 60 seconds. add(int timestamp) which adds timestamp in seconds in the hit counter count(int timestamp) which returns the number of hits that have been made in the last 60 seconds, given the current time is timestamp. You can assume that the timestamps passed into add and count are monotonically increasing. Constraints n ≤ 100,000 where n is the number of calls that are made to add and count Example 1 Input methods = ["constructor", "add", "add", "count", "add", "count"] arguments = [[], [10], [40], [40], [70], [100]]` Output [None, None, None, 2, None, 2] Explanation We create a HitCounter We add timestamp 10 to the data structure We add timestamp 40 to the data structure We count the number of timestamps that are within last 60 seconds of 40. There's 10 and 40 so we return 2 We add timestamp 70 to the data structure We count the number of timestamps that are within last 60 seconds of 100. There's 40 and 70 so we return 2

### Solution :

` ````
Solution in C++ :
class HitCounter {
public:
vector<int> v;
HitCounter() {
}
void add(int timestamp) {
v.push_back(timestamp);
}
int count(int timestamp) {
return v.end() - lower_bound(v.begin(), v.end(), timestamp - 60);
}
};
```

` ````
Solution in Python :
class HitCounter:
def __init__(self):
self.q = deque()
def _cleanup(self, timestamp):
while self.q and timestamp - self.q[0] > 60:
self.q.popleft()
def add(self, timestamp):
self.q.append(timestamp)
def count(self, timestamp):
self._cleanup(timestamp)
return len(self.q)
```

## View More Similar Problems

## Poisonous Plants

There are a number of plants in a garden. Each of the plants has been treated with some amount of pesticide. After each day, if any plant has more pesticide than the plant on its left, being weaker than the left one, it dies. You are given the initial values of the pesticide in each of the plants. Determine the number of days after which no plant dies, i.e. the time after which there is no plan

View Solution →## AND xor OR

Given an array of distinct elements. Let and be the smallest and the next smallest element in the interval where . . where , are the bitwise operators , and respectively. Your task is to find the maximum possible value of . Input Format First line contains integer N. Second line contains N integers, representing elements of the array A[] . Output Format Print the value

View Solution →## Waiter

You are a waiter at a party. There is a pile of numbered plates. Create an empty answers array. At each iteration, i, remove each plate from the top of the stack in order. Determine if the number on the plate is evenly divisible ith the prime number. If it is, stack it in pile Bi. Otherwise, stack it in stack Ai. Store the values Bi in from top to bottom in answers. In the next iteration, do the

View Solution →## Queue using Two Stacks

A queue is an abstract data type that maintains the order in which elements were added to it, allowing the oldest elements to be removed from the front and new elements to be added to the rear. This is called a First-In-First-Out (FIFO) data structure because the first element added to the queue (i.e., the one that has been waiting the longest) is always the first one to be removed. A basic que

View Solution →## Castle on the Grid

You are given a square grid with some cells open (.) and some blocked (X). Your playing piece can move along any row or column until it reaches the edge of the grid or a blocked cell. Given a grid, a start and a goal, determine the minmum number of moves to get to the goal. Function Description Complete the minimumMoves function in the editor. minimumMoves has the following parameter(s):

View Solution →## Down to Zero II

You are given Q queries. Each query consists of a single number N. You can perform any of the 2 operations N on in each move: 1: If we take 2 integers a and b where , N = a * b , then we can change N = max( a, b ) 2: Decrease the value of N by 1. Determine the minimum number of moves required to reduce the value of N to 0. Input Format The first line contains the integer Q.

View Solution →