Question

933. Number of Recent Calls

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Description

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 <= 109
• Each test case will call ping with strictly increasing values of t.
• At most 104 calls will be made to ping.

Solutions

Solution 1

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

class RecentCounter {
  private int[] s = new int[10010];
  private int idx;

  public RecentCounter() {
  }

  public int ping(int t) {
    s[idx++] = t;
    return idx - search(t - 3000);
  }

  private int search(int x) {
    int left = 0, right = idx;
    while (left < right) {
      int mid = (left + right) >> 1;
      if (s[mid] >= x) {
        right = mid;
      } else {
        left = mid + 1;
      }
    }
    return left;
  }
}

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

class RecentCounter {
public:
  queue<int> q;

  RecentCounter() {
  }

  int ping(int t) {
    q.push(t);
    while (q.front() < t - 3000) q.pop();
    return q.size();
  }
};

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

type RecentCounter struct {
  q []int
}

func Constructor() RecentCounter {
  return RecentCounter{[]int{}}
}

func (this *RecentCounter) Ping(t int) int {
  this.q = append(this.q, t)
  for this.q[0] < t-3000 {
    this.q = this.q[1:]
  }
  return len(this.q)
}

/**
 * Your RecentCounter object will be instantiated and called as such:
 * obj := Constructor();
 * param_1 := obj.Ping(t);
 */

class RecentCounter {
  private queue: number[];

  constructor() {
    this.queue = [];
  }

  ping(t: number): number {
    this.queue.push(t);
    while (this.queue[0] < t - 3000) {
      this.queue.shift();
    }
    return this.queue.length;
  }
}

/**
 * Your RecentCounter object will be instantiated and called as such:
 * var obj = new RecentCounter()
 * var param_1 = obj.ping(t)
 */

use std::collections::VecDeque;
struct RecentCounter {
  queue: VecDeque<i32>,
}

/**
 * `&self` means the method takes an immutable reference.
 * If you need a mutable reference, change it to `&mut self` instead.
 */
impl RecentCounter {
  fn new() -> Self {
    Self {
      queue: VecDeque::new(),
    }
  }

  fn ping(&mut self, t: i32) -> i32 {
    self.queue.push_back(t);
    while let Some(&v) = self.queue.front() {
      if v >= t - 3000 {
        break;
      }
      self.queue.pop_front();
    }
    self.queue.len() as i32
  }
}/**
 * Your RecentCounter object will be instantiated and called as such:
 * let obj = RecentCounter::new();
 * let ret_1: i32 = obj.ping(t);
 */

var RecentCounter = function () {
  this.q = [];
};

/**
 * @param {number} t
 * @return {number}
 */
RecentCounter.prototype.ping = function (t) {
  this.q.push(t);
  while (this.q[0] < t - 3000) {
    this.q.shift();
  }
  return this.q.length;
};

/**
 * Your RecentCounter object will be instantiated and called as such:
 * var obj = new RecentCounter()
 * var param_1 = obj.ping(t)
 */

public class RecentCounter {
  private Queue<int> q = new Queue<int>();

  public RecentCounter() {

  }

  public int Ping(int t) {
    q.Enqueue(t);
    while (q.Peek() < t - 3000)
    {
      q.Dequeue();
    }
    return q.Count;
  }
}

/**
 * Your RecentCounter object will be instantiated and called as such:
 * RecentCounter obj = new RecentCounter();
 * int param_1 = obj.Ping(t);
 */

Solution 2

class RecentCounter:
  def __init__(self):
    self.s = []

  def ping(self, t: int) -> int:
    self.s.append(t)
    return len(self.s) - bisect_left(self.s, t - 3000)


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

class RecentCounter {
public:
  vector<int> s;

  RecentCounter() {
  }

  int ping(int t) {
    s.push_back(t);
    return s.size() - (lower_bound(s.begin(), s.end(), t - 3000) - s.begin());
  }
};

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

type RecentCounter struct {
  s []int
}

func Constructor() RecentCounter {
  return RecentCounter{[]int{}}
}

func (this *RecentCounter) Ping(t int) int {
  this.s = append(this.s, t)
  search := func(x int) int {
    left, right := 0, len(this.s)
    for left < right {
      mid := (left + right) >> 1
      if this.s[mid] >= x {
        right = mid
      } else {
        left = mid + 1
      }
    }
    return left
  }
  return len(this.s) - search(t-3000)
}

/**
 * Your RecentCounter object will be instantiated and called as such:
 * obj := Constructor();
 * param_1 := obj.Ping(t);
 */