Nice use of chunk_while
But instead of a.succ[-1], why not use a.pred

Thank you. The bug is fixed.

I've fixed a bug, try now. Also, you can print the input using Debug.Trace.

Attemped a solution in Purescript.
All attached tests pass.
I'm unable to reproduce failed hidden tests cases.

Error: 4 /= 5 3 /= 0 2 /= 1 0 /= 2 2 /= 1 6 /= 1 7 /= 3 4 /= 1 4 /= 1 4 /= 1
3 /= 2 1 /= 2 1 /= 0 4 /= 6 6 /= 3 2 /= 1 4 /= 2 3 /= 0 5 /= 2 4 /= 0
6 /= 0 4 /= 0 5 /= 3 1 /= 2 7 /= 3 3 /= 2 4 /= 1 4 /= 3 5 /= 2 0 /= 1
5 /= 1 6 /= 5 8 /= 5 6 /= 0 4 /= 1 5 /= 2 0 /= 2 5 /= 1 3 /= 2 1 /= 0
3 /= 5 5 /= 3 3 /= 1 5 /= 3 2 /= 1 3 /= 6 8 /= 1 2 /= 1 4 /= 3 6 /= 4
4 /= 3 5 /= 1 3 /= 1 2 /= 6 3 /= 1 6 /= 1 4 /= 1 7 /= 0 4 /= 5 5 /= 2
1 /= 0 4 /= 0 5 /= 1 6 /= 1 4 /= 3 5 /= 7 8 /= 2
at Object.exports.error (/home/codewarrior/purescript/output/Effect.Exception/foreign.js:8:10)
at /home/codewarrior/purescript/output/Test.Spec.QuickCheck/index.js:34:108
at /home/codewarrior/purescript/output/Test.Spec.QuickCheck/index.js:45:58
at run (/home/codewarrior/purescript/output/Effect.Aff/foreign.js:273:20)
at Object.run (/home/codewarrior/purescript/output/Effect.Aff/foreign.js:630:13)
at run (/home/codewarrior/purescript/output/Effect.Aff/foreign.js:951:21)
at runPar (/home/codewarrior/purescript/output/Effect.Aff/foreign.js:990:5)
at /home/codewarrior/purescript/output/Effect.Aff/foreign.js:1004:16
at runAsync (/home/codewarrior/purescript/output/Effect.Aff/foreign.js:98:20)
at run (/home/codewarrior/purescript/output/Effect.Aff/foreign.js:323:22)