findStart

findstart.js

function findStart(strArr) {
  const stations = strArr.slice(1).map((station) => station.split(':').map(parseInt))
  for (let i = 0; i < stations.length; i++) {
    for (let i = 0; i < stations.length; i++) {
      let curGal = 0
      let total = 0;
      for (let j = 0; j < stations.length; j++) {
        const [gallons] = stations[i + j % stations.length]
        const [_, needed] = stations[(i + j + 1) % stations.length]
        curGal += gallons;
        if (curGal < needed) {
          break;
        } else {
          total++;
          curGal -= needed;
        }
      }
      if (total === stations.length) {
        return i + 1;
      }
    }
  }
  return "impossible";
}