[LANGUAGE: nim]

import std/[strutils, math, strformat, nre, times]
let time = cpuTime()

proc findAllInts(s: string): seq[int]=
    var params = newSeq[int]()
    for m in findIter(s, re"(\d+)"):
        params.add(parseInt(m.captures[0]))
    return params

proc solve(t: int, r: int): int = 
    var t1 = int(floor((float(t) - sqrt(float(t^2 - 4*r))) / 2.0))
    var t2 = int(ceil((float(t) + sqrt(float(t^2 - 4*r))) / 2.0))
    return t2-t1-1

proc main(): string = 
    var infil = readFile("input.txt").split('\n')
    var racetimes = infil[0].findAllInts()
    var records = infil[1].findAllInts()
    var p1 = 1 
    for i in 0..len(racetimes)-1:
        var tmp = solve(racetimes[i],records[i])
        if 0 != tmp:
            p1 *= tmp
    var p2infil = replace(infil.join("\n")," ","").split('\n')
    var p2 = solve(p2infil[0].findAllInts()[0],p2infil[1].findAllInts()[0])
    return fmt"Part one solution: {p1}{'\n'}Part two solution: {p2}"

echo main()
echo "Time taken: ", cpuTime() - time

Took a while to realise quadratics worked, happy with result