c++ - 检测偶数和奇数 C++ vector 迭代器

Question

我进行了搜索，令我惊讶的是还没有人问过这个问题。我知道如何用一个简单的循环来完成它，用 vector 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.
}

抱歉没说清楚，我的意思是检测 vector 的索引是奇数还是偶数。

Answer 1

这是一种简单的方法:

{
  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？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;
}

在这里查看:http://ideone.com/jmlV5F