向量计数函数C ++ [英] vector count function C++

问题描述

我有一个向量

  vector< int& vec; 
  

它存储了随机数{5,7,8,9,13,15,17} p>

并且我有一个向量，如果它们是素数，则将前一个向量的数字计算为1或0。

  vector< int> vec_prime_number; 
  

所以对于前一个，它将是{1,1,0,0,1,0,1 }

我试图使用count函数只保存素数。我会遇到一些问题。

理想情况下，我想让vec有
{5，7，13，17 } //换句话说，它只有素数

我尝试过像

这样的东西。

  int cnt = count（vec.begin（），vec.end（），vec_prime_number（））
  

但我不能得到任何它的工作。

解决方案

std的文档： ：count 说：

返回范围[first，last] val。

，因此您应该使用以下内容，以获取素数的数字：

  int cnt = count（vec_prime_number.begin（），vec_prime_number.end（），1）; 
  

为你可以看到。

I have a vector

vector<int> vec;

it's storing random numbers {5, 7, 8, 9, 13, 15, 17}

and I have a vector that is evaluating the previous vector's numbers as 1 or 0 if they are a prime number or not

vector< int> vec_prime_number;

so for the previous it would be {1, 1, 0, 0, 1, 0, 1}

I'm trying to use the count function to save only the prime numbers in it. And I'm having some problems with doing it.

Ideally, I would like to make it so that vec has {5, 7, 13, 17} //in other words, only prime numbers in it

I've tried stuff like

int cnt = count(vec.begin(), vec.end(), vec_prime_number())

but I can't get any of it to work. Any ideas on how to get count to store only the prime numbers?

解决方案

The documentation of std::count says:

Returns the number of elements in the range [first,last) that compare equal to val.

so you should use something along the lines of the following, to get the number of prime numbers:

int cnt = count(vec_prime_number.begin(), vec_prime_number.end(), 1);

as you can see.

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