933 Number of Recent Calls 最近的请求次数
Description:
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:
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.
题目描述:
写一个 RecentCounter 类来计算最近的请求。
它只有一个方法：ping(int t)，其中 t 代表以毫秒为单位的某个时间。
返回从 3000 毫秒前到现在的 ping 数。
任何处于 [t - 3000, t] 时间范围之内的 ping 都将会被计算在内，包括当前（指 t 时刻）的 ping。
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]
提示：
每个测试用例最多调用 10000 次 ping。
每个测试用例会使用严格递增的 t 值来调用 ping。
每次调用 ping 都有 1 <= t <= 10^9。
思路:
维护一个长度为 3000的滑动窗口, 可用队列实现
时间复杂度O(n), 空间复杂度O(1)
代码:
C++:
class RecentCounter
{
public:
RecentCounter() {}
int ping(int t)
{
q.push(t);
while (t - 3000 > q.front()) q.pop();
return q.size();
}
private:
queue q;
};
/**
* Your RecentCounter object will be instantiated and called as such:
* RecentCounter* obj = new RecentCounter();
* int param_1 = obj->ping(t);
*/
Java:
class RecentCounter {
private Queue queue;
public RecentCounter() {
queue = new LinkedList<>();
}
public int ping(int t) {
queue.offer(t);
while (queue.peek() < t - 3000) queue.poll();
return queue.size();
}
}
/**
* Your RecentCounter object will be instantiated and called as such:
* RecentCounter obj = new RecentCounter();
* int param_1 = obj.ping(t);
*/
Python:
class RecentCounter:
def __init__(self):
self.queue = collections.deque()
def ping(self, t: int) -> int:
self.queue.append(t)
while self.queue[0] < t - 3000:
self.queue.popleft()
return len(self.queue)
# Your RecentCounter object will be instantiated and called as such:
# obj = RecentCounter()
# param_1 = obj.ping(t)