How to remove elements from container is a common C++ interview question, so you can earn some brownie points if you read this page carefully.

如何从容器中删除元素是C ++常见的面试问题，因此，如果仔细阅读此页，可以赚取布朗尼积分。

The erase–remove idiom is a C++ technique to eliminate elements that fulfill a certain criterion from a container. However, it is possible to eliminate elements with traditional hand-written loop, but the erase–remove idiom has several advantages.

删除删除惯用语是一种C ++技术，用于从容器中删除满足特定条件的元素。 但是，可以使用传统的手写循环来消除元素，但是“擦除-删除”这一惯用法具有多个优点。

比较方式 (Comparison)

// Using a hand-written loop
std::vector<int> v = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
for (auto iter = v.cbegin(); iter < v.cend(); /*iter++*/)
{if (is_odd(*iter)){iter = v.erase(iter);}else{++iter;}
}// Using the erase–remove idiom
std::vector<int> v = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
v.erase(std::remove_if(v.begin(), v.end(), is_odd), v.end());

As you can see, the code with hand-written loop requires a bit more typing, but it also has a performance issue. Each erase call has to move forward all the elements after the deleted one, to avoid “gaps” in the collection. Calling erase multiple times on the same container generates lots of overhead of moving the elements.

如您所见，带有手写循环的代码需要更多的输入，但同时也存在性能问题。 每个erase调用都必须将所有元素移到已删除元素之后，以免集合中出现“空白”。 在同一容器上多次调用erase产生大量移动元素的开销。

On the other hand, the code with the erase–remove idiom is not only more expressive, but it also is more efficient. First, you use remove_if/remove to move all elements which don’t fit the remove criteria to the front of the range, keeping the relative order of the elements. So after calling remove_if/remove, a single call of erase deletes all remaining elements at the end of the range.

另一方面，带有“擦除-删除”惯用语的代码不仅更具表现力，而且效率更高。 首先，使用remove_if/remove将所有不符合删除条件的元素移动到范围的前面，并保持元素的相对顺序。 因此，在调用remove_if/remove ，一次erase删除范围末尾的所有剩余元素。

例 (Example)

#include <vector> // the general-purpose vector container
#include <iostream> // cout
#include <algorithm> // remove and remove_ifbool is_odd(int i)
{return (i % 2) != 0;
}void print(const std::vector<int> &vec)
{for (const auto& i : vec)std::cout << i << ' ';std::cout << std::endl;
}int main()
{// initializes a vector that holds the numbers from 1-10.std::vector<int> v = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };print(v);// removes all elements with the value 5v.erase(std::remove(v.begin(), v.end(), 5), v.end());print(v);// removes all odd numbersv.erase(std::remove_if(v.begin(), v.end(), is_odd), v.end());print(v);// removes multiples of 4 using lambdav.erase(std::remove_if(v.begin(), v.end(), [](int n) { return (n % 4) == 0; }), v.end());print(v);return 0;
}/*
Output:
1 2 3 4 5 6 7 8 9 10
1 2 3 4 6 7 8 9 10
2 4 6 8 10
2 6 10
*/

资料来源 (Sources)

“Erase–remove idiom” Wikipedia: The Free Encyclopedia. Wikimedia Foundation, Inc. en.wikipedia.org/wiki/Erase-remove_idiom

“删除擦除成语”维基百科：免费百科全书。 Wikimedia Foundation，Inc. zh.wikipedia.org/wiki/Erase-remove_idiom

Meyers, Scott (2001). Effective STL: 50 Specific Ways to Improve Your Use of the Standard Template Library. Addison-Wesley.

迈耶斯·斯科特(2001)。 有效的STL：50种提高标准模板库使用率的特定方法。 艾迪生-韦斯利。

翻译自: https://www.freecodecamp.org/news/how-to-remove-elements-from-a-container-in-c/