The itk::ImageRandomNonRepeatingIterator works by creating a random permutation of the image pixels and then using that to control the order in which it accesses them. The classes NodeOfPermutation and RandomPermutation are used to support that. RandomPermutation is basically container which holds NodeOfPermutation objects. The node class overloads the < operator, which allows the sort algorithm from the STL to be used on it.
Definition at line 40 of file itkImageRandomNonRepeatingConstIteratorWithIndex.h.