#include "seats.h"
#include <algorithm>
#include <utility>
constexpr int dx[] = { -1, 0, 1, 0}, dy[] = {0, -1, 0, 1};
int seg[4000005], cnt[4000005], lazy[4000005], n, m;
std::vector<std::pair<int, int> > pos;
std::vector<std::vector<int> > arr;
inline bool in_grid(int x, int y) { return x >= 0 && x < n && y >= 0 && y < m; }
inline void paint(int u, int x) { seg[u] += x; lazy[u] += x; }
void build(int u, int l, int r)
{
cnt[u] = r - l + 1;
if (l == r)
return;
int mid = l + r >> 1;
build(u << 1, l, mid);
build(u << 1 | 1, mid + 1, r);
}
void modify(int u, int l, int r, int L, int R, int x)
{
if (L > R)
return;
if (L <= l && r <= R)
{
paint(u, x);
return;
}
if (lazy[u])
{
paint(u << 1, lazy[u]);
paint(u << 1 | 1, lazy[u]);
lazy[u] = 0;
}
int mid = l + r >> 1;
if (L <= mid)
modify(u << 1, l, mid, L, R, x);
if (mid < R)
modify(u << 1 | 1, mid + 1, r, L, R, x);
seg[u] = std::min(seg[u << 1], seg[u << 1 | 1]);
cnt[u] = 0;
if (seg[u] == seg[u << 1])
cnt[u] += cnt[u << 1];
if (seg[u] == seg[u << 1 | 1])
cnt[u] += cnt[u << 1 | 1];
}
inline void modify(int x, int y, int coef)
{
int lim = n * m;
for (int i = 0; i < 2; i++)
{
int xx = x + dx[i], yy = y + dy[i];
if (in_grid(xx, yy))
lim = std::min(lim, arr[xx][yy]);
}
modify(1, 0, n * m - 1, arr[x][y], lim - 1, coef);
std::vector<int> adj;
for (int i = 0; i < 4; i++)
{
int xx = x + dx[i], yy = y + dy[i];
if (in_grid(xx, yy))
adj.push_back(arr[xx][yy]);
}
std::sort(adj.begin(), adj.end());
if (adj.size() > 1)
modify(1, 0, n * m - 1, adj[1], arr[x][y] - 1, coef);
}
void give_initial_chart(int H, int W, std::vector<int> R, std::vector<int> C)
{
n = H;
m = W;
arr.resize(n, std::vector<int>(m));
for (int i = 0; i < R.size(); i++)
{
arr[R[i]][C[i]] = i;
pos.emplace_back(R[i], C[i]);
}
build(1, 0, n * m - 1);
for (int i = 0; i < n; i++)
{
for (int j = 0; j < m; j++)
modify(i, j, 1);
}
}
int swap_seats(int a, int b)
{
std::vector<std::pair<int, int> > vec;
auto add = [&] (int x, int y)
{
vec.emplace_back(x, y);
for (int i = 0; i < 4; i++)
{
int xx = x + dx[i], yy = y + dy[i];
if (in_grid(xx, yy))
vec.emplace_back(xx, yy);
}
};
add(pos[a].first, pos[a].second);
add(pos[b].first, pos[b].second);
std::sort(vec.begin(), vec.end());
vec.erase(std::unique(vec.begin(), vec.end()), vec.end());
for (auto &it : vec)
modify(it.first, it.second, -1);
std::swap(pos[a], pos[b]);
arr[pos[a].first][pos[a].second] = a;
arr[pos[b].first][pos[b].second] = b;
for (auto &it : vec)
modify(it.first, it.second, 1);
return seg[1] == 1 ? cnt[1] : 0;
}
