#include <cstdlib>
#include <algorithm>
#include <iterator>

template<typename RandomAccessIterator>
void knuthShuffle(RandomAccessIterator begin, RandomAccessIterator end) {
  for(unsigned int n = end - begin - 1; n >= 1; --n) {
    unsigned int k = rand() % (n + 1);
    if(k != n) {
      std::iter_swap(begin + k, begin + n);
    }
  }
}