The predicate to sort by.
The swapping strategy to use.
The random-access range to reorder.
The index of the element that should be in sorted position after the function is done.
a slice from r[0] to r[nth], excluding r[nth] itself.
Stable topN has not been implemented yet.
int[] v = [ 25, 7, 9, 2, 0, 5, 21 ]; topN!"a < b"(v, 100); assert(v == [ 25, 7, 9, 2, 0, 5, 21 ]); auto n = 4; topN!((a, b) => a < b)(v, n); assert(v[n] == 9);
Reorders the range r using swap such that r[nth] refers to the element that would fall there if the range were fully sorted.
It is akin to Quickselect, and partitions r such that all elements e1 from r[0] to r[nth] satisfy !less(r[nth], e1), and all elements e2 from r[nth] to r[r.length] satisfy !less(e2, r[nth]). Effectively, it finds the nth + 1 smallest (according to less) elements in r. Performs an expected O(r.length) (if unstable) or O(r.length * log(r.length)) (if stable) evaluations of less and swap.
If n >= r.length, the algorithm has no effect and returns r[0 .. r.length].