Question

剑指 Offer II 042. 最近请求次数

题目描述

写一个 RecentCounter 类来计算特定时间范围内最近的请求。

请实现 RecentCounter 类：

• RecentCounter() 初始化计数器，请求数为 0 。
• int ping(int t) 在时间 t 添加一个新请求，其中 t 表示以毫秒为单位的某个时间，并返回过去 3000 毫秒内发生的所有请求数（包括新请求）。确切地说，返回在 [t-3000, t] 内发生的请求数。

保证 每次对 ping 的调用都使用比之前更大的 t 值。

 

示例：

输入：
inputs = ["RecentCounter", "ping", "ping", "ping", "ping"]
inputs = [[], [1], [100], [3001], [3002]]
输出：
[null, 1, 2, 3, 3]

解释：
RecentCounter recentCounter = new RecentCounter();
recentCounter.ping(1);   // requests = [1]，范围是 [-2999,1]，返回 1
recentCounter.ping(100);   // requests = [1, 100]，范围是 [-2900,100]，返回 2
recentCounter.ping(3001);  // requests = [1, 100, 3001]，范围是 [1,3001]，返回 3
recentCounter.ping(3002);  // requests = [1, 100, 3001, 3002]，范围是 [2,3002]，返回 3

 

提示：

• 1 <= t <= 109
• 保证每次对 ping 调用所使用的 t 值都 严格递增
• 至多调用 ping 方法 104 次

 

注意：本题与主站 933 题相同： https://leetcode.cn/problems/number-of-recent-calls/

解法

方法一

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 Deque<Integer> q;

  public RecentCounter() {
    q = new LinkedList<>();
  }

  public int ping(int t) {
    q.offerLast(t);
    while (q.peekFirst() < t - 3000) {
      q.pollFirst();
    }
    return q.size();
  }
}

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

class RecentCounter {
public:
  deque<int> q;

  RecentCounter() {
  }

  int ping(int t) {
    q.push_back(t);
    while (q.front() < t - 3000) {
      q.pop_front();
    }
    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{
    q: []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:len(this.q)]
  }
  return len(this.q)
}

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

class RecentCounter {
  stack: Array<number>;
  cnt: number;
  constructor() {
    this.stack = [];
    this.cnt = 0;
  }

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

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)
 */