giles
e057d9f18f
Some checks failed
Test, Build, and Deploy / test-build-deploy (push) Failing after 25s
Standard in-place next-permutation (Narayana's algorithm):
let next_perm a =
let n = Array.length a in
let i = ref (n - 2) in
while !i >= 0 && a.(!i) >= a.(!i + 1) do i := !i - 1 done;
if !i < 0 then false
else begin
let j = ref (n - 1) in
while a.(!j) <= a.(!i) do j := !j - 1 done;
swap a.(!i) a.(!j);
reverse a (!i + 1) (n - 1);
true
end
Starting from [1;2;3;4;5], next_perm returns true 119 times then
false (when reverse-sorted). 5! - 1 = 119.
Tests guarded `while … && a.(!i) … do` loops that rely on the
iter-242 short-circuit fix.
156 baseline programs total.
31 lines
623 B
OCaml
31 lines
623 B
OCaml
let next_perm a =
|
|
let n = Array.length a in
|
|
let i = ref (n - 2) in
|
|
while !i >= 0 && a.(!i) >= a.(!i + 1) do
|
|
i := !i - 1
|
|
done;
|
|
if !i < 0 then false
|
|
else begin
|
|
let j = ref (n - 1) in
|
|
while a.(!j) <= a.(!i) do
|
|
j := !j - 1
|
|
done;
|
|
let t = a.(!i) in a.(!i) <- a.(!j); a.(!j) <- t;
|
|
let lo = ref (!i + 1) and hi = ref (n - 1) in
|
|
while !lo < !hi do
|
|
let t = a.(!lo) in a.(!lo) <- a.(!hi); a.(!hi) <- t;
|
|
lo := !lo + 1;
|
|
hi := !hi - 1
|
|
done;
|
|
true
|
|
end
|
|
|
|
;;
|
|
|
|
let a = [| 1; 2; 3; 4; 5 |] in
|
|
let count = ref 0 in
|
|
while next_perm a do
|
|
count := !count + 1
|
|
done;
|
|
!count
|