[C++知识库]用LUA（和C++）刷PAT (Advanced Level) ——1033 To Fill or Not to Fill

-- ioread
local ioread = io.read('*a'):gmatch('%d+%p?%d*')
local function read_number()
    return tonumber(ioread())
end

--para
local Cmax = read_number() D = read_number() Davg = read_number() N = read_number() Dmax = Cmax*Davg
local stations = {}
local C = 0 cost = 0 Dis = 0 current_station = 1

--logic

function getNextStation()
    local current_price = stations[current_station].price
    local found_station = nil found_index = 0
    for index = current_station + 1, N do
        local station = stations[index]
        if station.distance - Dis > Dmax then
            break;
        end
        if station.price < current_price then
            return index;
        end
        if not found_station or station.price < found_station.price then
            found_station = station
            found_index = index
        end
    end
    
    if Dis + Dmax >= D or not found_station then
        return nil
    end
    
    return found_index
end

function update(station_index, is_better)
    -- add gas before leave
    local station = stations[station_index]
    local Ctarget = is_better and ((station.distance - Dis) / Davg) or Cmax
    cost = cost + (Ctarget - C) * stations[current_station].price
    C = Ctarget
    
    -- go to next station
    C = C - (station.distance - Dis) / Davg
    Dis = station.distance
    current_station = station_index
end

--main
for _ = 1, N do
    local price = read_number()
    local distance = read_number()
    if distance >= 0 and distance <= D then
        table.insert(stations, {price = price, distance = distance})
    end
end

table.sort(stations, function(a, b) return a.distance < b.distance end)

if stations[1].distance > 0 then
    print("The maximum travel distance = 0.00")
    return
end

for next_station in getNextStation do
    update(next_station, stations[next_station].price < stations[current_station].price)
end

if Dis + Dmax >= D then
    Clack = (D - Dis) / Davg - C
    cost = cost + Clack * stations[current_station].price
    print(string.format("%.2f", cost))
else
    print("The maximum travel distance = " .. string.format("%.2f", Dis + Dmax))
end