Get required cars number

cars.go

func getRequiredCarsNum2(busCap, carCap int, stations []int) int {
	cars := 0
	busUsed := false
	resortFullBus := -1
	resortHalfBus := -1
	halfBusMax := 0

	for i, p := range stations {
		// Don't care about empty stations
		if p == 0 {
			continue
		}

		// If we didn't use the bus yet, consider it
		if !busUsed {
			if p >= busCap {
				if (p-busCap)%carCap == 0 {
					// This station is a great fit for the bus, so, use it
					p -= busCap
					busUsed = true
				} else if resortFullBus == -1 && p%carCap != 0 {
					// Remember the first station which is not a great fit for cars only:
					// if there's no perfect fit for the bus, we'll resort to that
					resortFullBus = i
				}
			}
			if p > halfBusMax {
				// Also remember the last last resort, for which the bus won't be full,
				// but at least it will carry maximum number of passengers
				halfBusMax = p
				resortHalfBus = i
			}
		}

		cars += getCarsCnt(p, carCap)
	}

	// If we haven't used the bus (because there was no perfect fit for it), use
	// resortFullBus
	if len(stations) > 0 && !busUsed {
		// First, try to resort to some station which would fill the bus fully
		resort := resortFullBus

		// If it wasn't successful, resort to half-filled bus
		if resort == -1 {
			resort = resortHalfBus
		}

		// If that is not successful either, it doesn't matter where to send the bus,
		// just pick the first station
		if resort == -1 {
			resort = 0
		}

		// Fixup cars number by reconsidering the bus for resort
		p := stations[resort]
		cars -= getCarsCnt(p, carCap)
		p -= busCap
		if p < 0 {
			p = 0
		}
		cars += getCarsCnt(p, carCap)
	}

	return cars
}

func getCarsCnt(passengers, carCap int) int {
	return (passengers + (carCap - 1)) / carCap
}