std::erase_if (std::set)

< cpp‎ | container‎ | set

 
C++
 
容器库
 
std::set
 
定义于头文件 <set>
template< class Key, class Compare, class Alloc, class Pred >

typename std::set<Key,Compare,Alloc>::size_type

    erase_if(std::set<Key,Compare,Alloc>& c, Pred pred);
 (C++20 起)

从容器中擦除所有满足谓词 pred 的元素。等价于 

auto old_size = c.size();
for (auto i = c.begin(), last = c.end(); i != last; ) {
  if (pred(*i)) {
    i = c.erase(i);
  } else {
    ++i;
  }
}
return old_size - c.size();

参数

c - 要从中擦除的元素
pred - 若应该擦除元素则对它返回 true 的谓词

返回值

擦除的元素数。

复杂度

线性。

示例

运行此代码
#include <set>
#include <iostream>
 
template<typename Os, typename Container>
inline Os& operator<<(Os& os, Container const& container)
{
    os << "{ ";
    for (const auto& item : container) {
        os << item << ' ';
    }
    return os << "}";
}
 
int main()
{
    std::set data { 0, 1, 2, 3, 3, 4, 5, 5, 6, 6, 7 };
    std::cout << "Original:\n" << data << '\n';
 
    auto divisible_by_3 = [](auto const& x) { return (x % 3) == 0; };
 
    const auto count = std::erase_if(data, divisible_by_3);
 
    std::cout << "Erase all items divisible by 3:\n" << data << '\n'
              << count << " items erased.\n";
}

输出： 

Original:
{ 0 1 2 3 4 5 6 7 }
Erase all items divisible by 3:
{ 1 2 4 5 7 }
3 items erased.

参阅

 移除满足特定判别标准的元素
(函数模板)