c – 使用std算法将容器分区/批处理/块化为相等大小的块

#include <Cassert>
#include <vector>
#include <algorithm>

template< typename T >
std::vector< std::vector< T > > chunk( std::vector<T> const& container,size_t chunk_size )
{
  return std::vector< std::vector< T > >();
}

int main()
{
  int i = 0;
  const size_t test_size = 11;
  std::vector<int> container(test_sizE);
  std::generate_n( std::begin(container),test_size,[&i](){ return ++i; } );

  auto chunks = chunk( container,3 );

  assert( chunks.size() == 4 && "should be four chunks" );
  assert( chunks[0].size() == 3 && "first several chunks should have the ideal chunk size" );
  assert( chunks.BACk().size() == 2 && "last chunk should have the remaining 2 elements" );

  return 0;
}

这个问题似乎是std :: for_each的一个变种,你想要操作的“每个”是你的集合的间隔.因此,您更愿意编写一个lambda(或函数),它接受两个迭代器定义每个间隔的开始和结束,并将该lambda /函数传递给您的算法.

这就是我想出来的……

// (Headers omitted)

template < typename Iterator >
void for_each_interval(
    Iterator begin,Iterator end,size_t interval_size,std::function<void( Iterator,Iterator )> operation )
{
  auto to = begin;

  while ( to != end )
  {
    auto from = to;

    auto counter = interval_size;
    while ( counter > 0 && to != end )
    {
      ++to;
      --counter;
    }

    operation( from,to );
  }
}

(我希望std :: advance会处理使用COunter递增的内部循环,但不幸的是它盲目地超越了结尾[我很想写我自己的smart_advance模板来封装它].如果这样可行的话,它会减少大约一半的代码量！)

现在为一些代码来测试它…

// (Headers omitted)

int main( int argc,char* argv[] )
{
  // Some test data
  int foo[10] = { 0,1,2,3,4,5,6,7,8,9 };
  std::vector<int> my_data( foo,foo + 10 );
  size_t const interval = 3;

  typedef decltype( my_data.begin() ) iter_t;
  for_each_interval<iter_t>( my_data.begin(),my_data.end(),interval,[]( iter_t from,iter_t to )
    {
      std::cout << "Interval:";
      std::for_each( from,to,[&]( int val )
        {
          std::cout << " " << val;
        } );
      std::cout << std::endl;
    } );
}

这会产生以下输出,我认为它代表你想要的：

Interval: 0 1 2
Interval: 3 4 5
Interval: 6 7 8
Interval: 9