检测偶数和奇数C++向量迭代器

Question

我搜索过,我很惊讶这还没有被问到.我知道如何用一个简单的循环来做,用矢量迭代器怎么样？

for( std::vector<int>::iterator it = somevector.begin(); it != somevector.end(); ++it )
{
    //Conditions stating a certain vector has an even or odd index.
}

很抱歉没有澄清,我的意思是检测向量的索引是奇数还是偶数.

Answer 1

这将是一个简单的方法:

{
  bool is_even = true;
  for (const auto& v: somevector) {
    if (is_even) even_handler(v);
    else         odd_handler(v);
    is_even = !is_even;
  }
}

想要更复杂的解决方案吗？没问题:

#include <iostream>
#include <string>
#include <utility>
#include <vector>
using std::next;
template<typename Iter, typename Func, typename...Funcs>
void RotateHandlers(Iter b, Iter e, Func f, Funcs...fs) {
    if (b != e) {
        f(*b);
        RotateHandlers(next(b), e, fs..., f);
    }
}

int main() {
    std::vector<std::string> v({"Hello", "world", "it's", "really", "great", "to", "be", "here"});
    RotateHandlers(v.begin(), v.end(),
      [](const std::string& s){std::cout << "First|" << s << std::endl;},
      [](const std::string& s){std::cout << "Then |" << s << std::endl;},
      [](const std::string& s){std::cout << "And  |" << s << std::endl
                                         << "     |" << std::string(s.size(), '-') << std::endl;}
    );
    return 0;
}

请在此处查看:http://ideone.com/jmlV5F