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| #pragma GCC optimize(2)
#include <iostream>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <cstdlib>
#include <algorithm>
#include <vector>
#include <queue>
#define mkp(a, b) make_pair(a, b)
#define DD double
#define pii pair<int, int>
#define rint register int
#define MAXN (4000000 + 5)
#define MAXC (200000 + 5)
#define MAXL (20)
#define INF (0x7ffffff)
using namespace std;
const int xy[4][2] = {{1, 0}, {-1, 0}, {0, 1}, {0, -1}};
struct edg
{
int from, to, cost, next;
edg() {}
edg(int f, int t, int c): from(f), to(t), cost(c) {}
} b[MAXC << 1];
int g[MAXC], cntb, n, h, w, vis[MAXN], col[MAXN], city[MAXC], fa[MAXC], size[MAXN], dis[MAXN];
int d[MAXC][MAXL], maxc[MAXC][MAXL], lgn, deep[MAXC], nc;
vector<edg> rb[MAXN];
inline int pti(const pii x)
{ return (x.first - 1) * w + x.second; }
inline pii itp(const int x)
{ return mkp(ceil((DD)x / w), x - ceil((DD)x / w) * w + w); }
inline int max(const int x, const int y)
{ return x > y ? x : y; }
inline int min(const int x, const int y)
{ return x < y ? x : y; }
inline void adn(const int from, const int to, const int cost)
{
b[++cntb].next = g[from];
b[cntb].from = from, b[cntb].to = to, b[cntb].cost = cost;
g[from] = cntb;
}
inline bool pd(const pii x)
{ return (x.first <= h && x.first >= 1 && x.second <= w && x.second >= 1 && vis[pti(x)] >= 0); }
inline void init(const int s, const int c)
{
queue<int> q;
q.push(s);
col[s] = c;
while (!q.empty())
{
const int dq = q.front();
q.pop();
if (vis[dq] > 0)
++size[c];
for (rint i = 0; i < 4; i++)
{
pii ndq = itp(dq);
ndq.first += xy[i][0], ndq.second += xy[i][1];
if (!pd(ndq))
continue;
if (!col[pti(ndq)])
col[pti(ndq)] = c, q.push(pti(ndq));
}
}
}
void bfs()
{
queue<int> q;
for (rint i = 1; i <= n; i++)
q.push(city[i]);
while (!q.empty())
{
int dq = q.front();
q.pop();
for (rint i = 0; i < 4; i++)
{
pii ndq = itp(dq);
ndq.first += xy[i][0], ndq.second += xy[i][1];
int idq = pti(ndq);
if (!pd(ndq) || vis[idq] == vis[dq])
continue;
if (vis[idq])
rb[col[dq]].push_back(edg(vis[dq], vis[idq], dis[idq] + dis[dq]));
else
{
vis[idq] = vis[dq];
dis[idq] = dis[dq] + 1;
q.push(idq);
}
}
}
}
int find(const int x)
{ return (x == fa[x] ? x : (fa[x] = find(fa[x]))); }
void uni(const int x, const int y)
{ fa[find(x)] = find(y); }
inline bool cmp(const edg x, const edg y)
{ return x.cost < y.cost; }
void kruskal(const int dqc)
{
sort(rb[dqc].begin(), rb[dqc].end(), cmp);
int cnt = 0;
for (rint i = 0, u, v; i < rb[dqc].size(); i++)
if (find(u = rb[dqc][i].from) != find(v = rb[dqc][i].to))
{
uni(u, v);
adn(u, v, rb[dqc][i].cost);
adn(v, u, rb[dqc][i].cost);
++cnt;
if (cnt == size[dqc] - 1)
break;
}
}
void dfs(int dq)
{
for (rint i = 1; i <= lgn; i++)
{
d[dq][i] = d[d[dq][i - 1]][i - 1];
maxc[dq][i] = max(maxc[dq][i - 1], maxc[d[dq][i - 1]][i - 1]);
}
for (rint i = g[dq]; i; i = b[i].next)
if (d[dq][0] != b[i].to)
{
d[b[i].to][0] = dq;
maxc[b[i].to][0] = b[i].cost;
deep[b[i].to] = deep[dq] + 1;
dfs(b[i].to);
}
}
int solve(int x, int y)
{
int re = 0;
if (deep[y] > deep[x])
swap(x, y);
for (rint i = lgn; i >= 0; i--)
if (deep[d[x][i]] >= deep[y])
re = max(re, maxc[x][i]), x = d[x][i];
if (x == y)
return re;
for (rint i = lgn; i >= 0; i--)
if (d[x][i] != d[y][i])
re = max(re, max(maxc[x][i], maxc[y][i])), x = d[x][i], y = d[y][i];
return max(re, max(maxc[x][0], maxc[y][0]));
}
int lg(int x)
{
int re = 0;
while ((1 << re) < x)
++re;
return re;
}
int main()
{
int q;
scanf("%d%d%d%d", &h, &w, &n, &q);
lgn = lg(n);
for (rint i = 1; i <= h; i++)
for (rint j = 1; j <= w; j++)
{
char x = 0;
while (x != '.' && x != '#')
scanf("%c", &x);
if (x == '.') vis[pti(mkp(i, j))] = 0;
else vis[pti(mkp(i, j))] = -1;
}
for (rint i = 1, srx, sry; i <= n; i++)
scanf("%d%d", &srx, &sry), vis[city[i] = pti(mkp(srx, sry))] = i;
for (rint i = 1; i <= n; i++)
if (!col[city[i]])
init(city[i], ++nc);
bfs();
for (rint i = 1; i <= n; i++) fa[i] = i;
for (rint i = 1; i <= nc; i++)
kruskal(i);
for (rint i = 1; i <= n; i++)
if (!d[i][0])
d[i][0] = i, deep[i] = 1, dfs(i);
for (rint i = 1, srx, sry; i <= q; i++)
{
scanf("%d%d", &srx, &sry);
if (col[city[srx]] != col[city[sry]])
puts("-1");
else
printf("%d\n", solve(srx, sry));
}
return 0;
}
|