# Sol

# include <bits/stdc++.h>
# define IL inline
# define RG register
# define Fill(a, b) memset(a, b, sizeof(a))
using namespace std;
typedef long long ll;

IL int Input(){
RG int x = 0, z = 1; RG char c = getchar();
for(; c < '0' || c > '9'; c = getchar()) z = c == '-' ? -1 : 1;
for(; c >= '0' && c <= '9'; c = getchar()) x = (x << 1) + (x << 3) + (c ^ 48);
return x * z;
}

const int maxn(2005);
const int maxm(4000005);
const int maxp(2e5 + 5);

struct Data{
int x, y;
};

struct Edge{
int v, w;
};

int k, n, m, vis[maxm], dis[maxm], qry, deep[maxp];
int fa[maxp], idx, posx[maxm], posy[maxm], st[19][maxp], mx[19][maxp];
int dx[4] = {0, 0, -1, 1}, dy[4] = {-1, 1};
bool wall[maxm];
char s[maxn];
vector <Edge> graph[maxp];
vector <Data> edge[maxm];
queue <int> q;

IL int Find(RG int x){
return x == fa[x] ? x : fa[x] = Find(fa[x]);
}

IL void Add(RG int u, RG int v, RG int w){
graph[u].push_back((Edge){v, w});
graph[v].push_back((Edge){u, w});
}

IL void Dfs(RG int u, RG int ff){
for(RG int i = 1; i <= 18; ++i){
st[i][u] = st[i - 1][st[i - 1][u]];
mx[i][u] = max(mx[i - 1][u], mx[i - 1][st[i - 1][u]]);
}
for(RG auto x: graph[u])
if(x.v != ff){
mx[0][x.v] = x.w, st[0][x.v] = u;
deep[x.v] = deep[u] + 1;
Dfs(x.v, u);
}
}

# define ID(i, j) ((i - 1) * m + j)

IL int Calc(RG int u, RG int v){
RG int ret = 0;
if(deep[u] < deep[v]) swap(u, v);
for(RG int j = 18; ~j; --j)
if(deep[st[j][u]] >= deep[v]){
ret = max(ret, mx[j][u]);
u = st[j][u];
}
if(u == v) return ret;
for(RG int j = 18; ~j; --j)
if(st[j][u] != st[j][v]){
ret = max(ret, max(mx[j][u], mx[j][v]));
u = st[j][u], v = st[j][v];
}
return max(ret, max(mx[0][u], mx[0][v]));
}

int main(){
n = Input(), m = Input(), k = Input(), qry = Input();
for(RG int i = 1; i <= n; ++i){
scanf(" %s", s + 1);
for(RG int j = 1; j <= m; ++j){
++idx, posx[idx] = i, posy[idx] = j;
wall[idx] = s[j] == '#';
}
}
for(RG int i = 1; i <= k; ++i){
RG int px = Input(), py = Input(), id = ID(px, py);
vis[id] = fa[i] = i, dis[id] = 0, q.push(id);
}
while(!q.empty()){
RG int u = q.front(); q.pop();
for(RG int i = 0; i < 4; ++i){
RG int xx = posx[u] + dx[i], yy = posy[u] + dy[i];
if(xx < 1 || yy < 1 || xx > n || yy > m) continue;
RG int id = ID(xx, yy);
if(wall[id]) continue;
if(!vis[id]){
vis[id] = vis[u], dis[id] = dis[u] + 1;
q.push(id);
}
else edge[dis[id] + dis[u]].push_back((Data){vis[u], vis[id]});
}
}
for(RG int i = 0; i <= n * m; ++i)
for(RG auto v: edge[i]){
RG int fx = Find(v.x), fy = Find(v.y);
if(fx != fy) fa[fx] = fy, Add(v.x, v.y, i);
}
for(RG int i = 1; i <= k; ++i) if(!st[0][i]) Dfs(i, 0);
while(qry--){
RG int u = Input(), v = Input();
if(Find(u) != Find(v)) puts("-1");
else printf("%d\n", Calc(u, v));
}
return 0;
}


posted @ 2018-06-12 07:40  Cyhlnj  阅读(92)  评论(0编辑  收藏