Standard Template Library (STL) -
std::queue::empty
std::queue::empty
public member function - 公开成员函数
1. std::queue::empty
bool empty() const;
Test whether container is empty - 测试容器是否为空
检查底层的容器是否为空。
Returns whether the queue is empty: i.e. whether its size is zero.
返回队列是否为空:即队列大小是否为零。
This member function effectively calls member empty
of the underlying container object.
该成员函数有效地调用底层容器对象的成员 empty
。
2. Parameters
none - 无
3. Return value
true
if the underlying container’s size is 0, false
otherwise.
如果底层容器的大小为 0,则为 true
,否则为 false
。
若底层容器为空则为 true
,否则为 false
。
4. Examples
4.1 std::queue::empty
//============================================================================
// Name : std::queue::empty
// Author : Yongqiang Cheng
// Version : Feb 22, 2020
// Copyright : Copyright (c) 2019 Yongqiang Cheng
// Description : Hello World in C++, Ansi-style
//============================================================================
#include <iostream> // std::cout
#include <queue> // std::queue
int main()
{
std::queue<int> queue_data;
int sum(0);
for (int i = 1; i <= 10; i++)
{
queue_data.push(i);
}
while (!queue_data.empty())
{
sum += queue_data.front();
queue_data.pop();
}
std::cout << "total: " << sum << '\n';
return 0;
}
The example initializes the content of the queue to a sequence of numbers (form 1 to 10). It then pops the elements one by one until it is empty and calculates their sum.
该示例将队列的内容初始化为一个数字序列 (格式为 1 到 10)。然后,将元素逐一弹出,直到元素为空,然后计算它们的总和。
total: 55
5. Complexity - 复杂度
Constant (calling empty
on the underlying container).
常数 (在底层容器上调用 empty
)。
6. Data races - 数据竞争
The container is accessed.
容器被访问。
7. Exception safety - 异常安全性
Provides the same level of guarantees as the operation performed on the container (no-throw guarantee for standard container types).
提供与在容器上执行的操作相同级别的保证 (标准容器类型的无抛出保证)。
assignment [ə'saɪnmənt]:n. 任务,布置,赋值
References
http://www.cplusplus.com/reference/queue/queue/empty/
https://en.cppreference.com/w/cpp/container/queue/empty