Function permutator::x_permutation_sync

pub fn x_permutation_sync<'a, T>(
    d: &'a [T], 
    result: Arc<RwLock<Vec<&'a T>>>, 
    t: impl FnMut(&[&T]) -> bool, 
    cb: impl FnMut()
)

A lexicographic ordered permutation based on “Algoritm X” published by Donald E. Knuth. page 20.

If order is not important, consider using heap permutation function instead. This function is 3 times slower than heap heap permutation in uncontroll test environment.

The algorithm work by simulate tree traversal where some branch can be skip altogether. This is archive by provided t function that take slice of partial result as parameter. If the partial result needed to be skip, return false. Otherwise, return true and the algorithm will call this function again when the branch is descended deeper. For example: First call to t may contain [1]. If t return true, it will be called again with [1, 2]. If it return true, and there’s leaf node, cb will be called with [1, 2]. On the other hand, if t is called with [1, 3] and it return false, it won’t call the callback. If t is called with [4] and it return false, it won’t try to traverse deeper even if there’re [4, 5], or [4, 6]. It will skip altogether and call t with [7]. The process goes on until every branch is traversed.

Example

See x_permutation document for example. It’s the same except the way it return result.

Parameters

• d : &[T] - A data to get a permutation.
• result : Arc<RwLock<Vec<&T>>> - A result container. The result will be overwritten on each call to callback.
• t : FnMut(&[&T]) -> bool - A function for checking whether to traverse the branch. It shall return true if the branch need to be traversed.
• cb : FnMut() - A callback function that notify caller that new result is available.