#include "books.h"
#include <cstdlib>
#include <queue>
#include <utility>
const int MAXN = 1e6;
int belongsTo[MAXN];
std::pair<int, int> cycInter[MAXN];
std::queue<std::pair<int, int>> toCheck;
void processcycle(int cycle, int &left, int &right)
{
if (cycInter[cycle].first < left)
{
toCheck.emplace(cycInter[cycle].first, left);
left = cycInter[cycle].first;
}
if (cycInter[cycle].second > right)
{
toCheck.emplace(right, cycInter[cycle].second);
right = cycInter[cycle].second;
}
}
std::pair<int, int> check(int doneLeft, int doneRight)
{
int left = doneLeft, right = doneRight;
while (!toCheck.empty())
{
std::pair<int, int> checkingInter = toCheck.front();
toCheck.pop();
for (int iTable = checkingInter.first; iTable < checkingInter.second; iTable++)
processcycle(belongsTo[iTable], left, right);
}
return { left, right };
}
long long minimum_walk(std::vector<int> p, int s)
{
int tables = p.size();
std::fill_n(belongsTo, tables, -1);
long long minWalk = 0;
int cycles = 0;
for (int iTable = 0; iTable < tables; iTable++)
if (belongsTo[iTable] == -1)
{
int leftMost = tables, rightMost = 0;
int curTable = iTable;
while (belongsTo[curTable] == -1)
{
leftMost = std::min(leftMost, curTable);
rightMost = std::max(rightMost, curTable);
belongsTo[curTable] = cycles;
minWalk += (long long)std::abs(curTable - p[curTable]);
curTable = p[curTable];
}
cycInter[cycles] = { leftMost, rightMost + 1 };
cycles++;
}
int endLeft = 0, endRight = tables;
while (endLeft < s && cycInter[belongsTo[endLeft]].second - cycInter[belongsTo[endLeft]].first == 1)
endLeft++;
while (endRight - 1 > s && cycInter[belongsTo[endRight - 1]].second - cycInter[belongsTo[endRight - 1]].first == 1)
endRight--;
toCheck.emplace(s, s + 1);
std::pair<int, int> done = check(s, s + 1);
while (done.first != endLeft || done.second != endRight)
{
long long costLeft = 0;
std::pair<int, int> moveLeft = done;
while (moveLeft.first != endLeft && moveLeft.second == done.second)
{
toCheck.emplace(moveLeft.first - 1, moveLeft.first);
costLeft += 2;
moveLeft = check(moveLeft.first - 1, moveLeft.second);
}
long long costRight = 0;
std::pair<int, int> moveRight = done;
while (moveRight.first == done.first && moveRight.second != endRight)
{
toCheck.emplace(moveRight.second, moveRight.second + 1);
costRight += 2;
moveRight = check(moveRight.first, moveRight.second + 1);
}
if (moveLeft == moveRight)
{
minWalk += std::min(costLeft, costRight);
done = moveLeft;
}
else
{
minWalk += costLeft + costRight;
done = { moveLeft.first, moveRight.second };
}
}
return minWalk;
}
