private static long SolveFast(long n, long m, List <long> a, List <long> b)
{
var sortedDays = new SortedSet <Day>(new DayComparer());
for (var i = 0; i < n; i++)
{
var day = new Day(i, a[i], b[i], 0);
sortedDays.Add(day);
}
var cTotal = 0L;
var aTotal = 0L;
for (var i = 0; i < n; i++)
{
cTotal += a[i] * b[i];
aTotal += a[i];
}
foreach (var day in sortedDays.ToList())
{
cTotal -= day.C;
aTotal -= day.A;
n--;
// C_average_adjusted = C_average * (1 - (M-BALLOON) / A_total)
// = C_day - B_day * BALLOON
// <=> BALLOON = (C_day - C_average * (1 - M / A_total)) / (C_average / A_total + B_day)
var balloonNeeded = n > 0
? (day.C - cTotal * 1.0 / n * (1 - m * 1.0 / aTotal)) / ((cTotal * 1.0 / n) / aTotal + day.B)
: day.A;
var balloon = Math.Min((long)Positiv(balloonNeeded), m);
if (balloon > 0)
{
sortedDays.Remove(day);
m -= balloon;
day.AddBalloon(balloon);
sortedDays.Add(day);
}
}
for (var k = m; k > 0; k--)
{
var day = sortedDays.Max;
sortedDays.Remove(day);
day.AddBalloon();
sortedDays.Add(day);
}
var nextSortedDays = new SortedSet <Day>(new NextBalloonDayComparer());
foreach (var day in sortedDays)
{
if (day.CanRemoveBalloon())
{
nextSortedDays.Add(day);
}
}
// switch
while (sortedDays.Max.C > nextSortedDays.Min.C + nextSortedDays.Min.B)
{
var day = sortedDays.Max;
sortedDays.Remove(day);
nextSortedDays.Remove(day);
var nextDay = nextSortedDays.Min;
sortedDays.Remove(nextDay);
nextSortedDays.Remove(nextDay);
day.AddBalloon();
sortedDays.Add(day);
nextSortedDays.Add(day);
nextDay.RemoveBalloon();
sortedDays.Add(nextDay);
if (day.CanRemoveBalloon())
{
nextSortedDays.Add(nextDay);
}
}
var res = sortedDays.Max.C;
return(res);
}