Nim

Got correct answer for part 1 on first try, but website rejected it. Wasted some time debugging and trying different methods. Only to have the same answer accepted minutes later. =(

proc isSafe(report: seq[int]): bool =
  let diffs = collect:
    for i, n in report.toOpenArray(1, report.high): n - report[i]
  (diffs.allIt(it > 0) or diffs.allIt(it < 0)) and diffs.allIt(it.abs in 1..3)

proc solve(input: string): AOCSolution[int, int] =
  let lines = input.splitLines()
  var reports: seq[seq[int]]
  for line in lines:
    reports.add line.split(' ').map(parseInt)

  for report in reports:
    if report.isSafe():
      inc result.part1
      inc result.part2
    else:
      for t in 0..report.high:
        var mReport = report
        mReport.delete t
        if mReport.isSafe():
          inc result.part2
          break

Codeberg repo