CF1320E Treeland and Viruses
CF1320E Treeland and Viruses
仔细观察题目,直接上虚树。
再考虑套路 dp
,发现有许多优先级不太好做。
考虑 spfa
,发现一个点被感染后,另外的病毒不能走这个点,不太好做。
考虑优先队列,每次取最优的点更新,显然正解。
时间复杂度 。
#include<bits/stdc++.h>
using namespace std;
//#define int long long
typedef long long ll;
#define ha putchar(' ')
#define he putchar('\n')
inline int read()
{
int x = 0, f = 1;
char c = getchar();
while (c < '0' || c > '9')
{
if (c == '-')
f = -1;
c = getchar();
}
while (c >= '0' && c <= '9')
x = x * 10 + c - '0', c = getchar();
return x * f;
}
inline void write(int x)
{
if(x < 0)
{
putchar('-');
x = -x;
}
if(x > 9)
write(x / 10);
putchar(x % 10 + '0');
}
const int _ = 2e5 + 10;
int n, Q, k, m, t, s[_], w[_];
bool vis[_];
int cnt, dfn[_], fa[_], siz[_], hson[_], top[_], dep[_];
vector<int> d[_], v, p, q, a, b, g[_];
bool cmp(int u, int v)
{
return dfn[u] < dfn[v];
}
void dfs1(int u, int D = 1)
{
dep[u] = D, siz[u] = 1, dfn[u] = ++cnt;
for(int v : d[u])
{
if(siz[v]) continue;
fa[v] = u;
dfs1(v, D + 1);
siz[u] += siz[v];
if(siz[hson[u]] < siz[v]) hson[u] = v;
}
}
void dfs2(int u, int tf)
{
top[u] = tf;
if(hson[u]) dfs2(hson[u], tf);
for(int v : d[u])
{
if(top[v]) continue;
dfs2(v, v);
}
}
int LCA(int u, int v)
{
// cout << "1\n";
while(top[u] != top[v])
{
// cout << "2\n";
if(dep[top[u]] < dep[top[v]]) swap(u, v);
u = fa[top[u]];
}
// cout << "3\n";
return dep[u] > dep[v] ? v : u;
}
int Dis(int x, int y)
{
return dep[x] + dep[y] - 2 * dep[LCA(x, y)];
}
void build()
{
q = p;
for(int x : p)
{
int lca = LCA(x, s[t]);
if(lca != s[t])
{
while(t && dep[s[t - 1]] >= dep[lca])
{
g[s[t]].push_back(s[t - 1]), g[s[t - 1]].push_back(s[t]);
--t;
}
if(s[t] != lca)
{
g[s[t]].push_back(lca), g[lca].push_back(s[t]);
s[t] = lca;
q.push_back(lca);
}
}
s[++t] = x;
}
if(t)
while (--t) g[s[t]].push_back(s[t + 1]), g[s[t + 1]].push_back(s[t]);
p = q;
}
struct abc
{
int d, i, x, r;
abc()
{
}
abc(int d, int i, int x) : d(d), i(i), x(x)
{
// if(!w[x])
// {
//// cout << x << "\n";
//// cout << "!!!!!!!!!\n";
// exit(0);
// }
r = d ? (d - 1) / w[x] : -1;
}
bool operator < (const abc o) const
{
return r == o.r ? i < o.i : r < o.r;
}
} dis[_];
struct Node
{
abc a; int id;
bool operator < (const Node &t) const
{
return a.r == t.a.r ? a.i > t.a.i : a.r > t.a.r;
}
};
void dij()
{
priority_queue<Node> q;
for(int x : p)
{
dis[x].r = dis[x].i = n;
vis[x] = 0;
}
for(int i = 0; i < a.size(); i++)
{
dis[a[i]] = abc(0, i + 1, a[i]);
q.push({dis[a[i]], a[i]});
}
while(!q.empty()) {
int x = q.top().id;
q.pop();
if (vis[x]) continue;
vis[x] = 1;
// cout <<x << "\n";
for (int y : g[x])
{
// cout << ": " << y << "\n";
abc nw = abc(dis[x].d + Dis(x, y), dis[x].i, dis[x].x);
if (nw < dis[y])
{
dis[y] = nw;
q.push({dis[y], y});
}
}
}
for(int x : b) write(dis[x].i), ha;
he;
}
signed main()
{
n = read();
for(int i = 1, u, v; i < n; ++i)
{
u = read(), v = read();
d[u].push_back(v);
d[v].push_back(u);
}
dfs1(1), dfs2(1, 1);
Q = read();
while(Q--)
{
k = read(), m = read();
v.clear(), p.clear(), a.clear(), q.clear(), b.clear();
for(int i = 1, x, y; i <= k; ++i)
{
x = read(), y = read();
a.push_back(x);
v.push_back(x), w[x] = y;
}
for(int i = 1, x; i <= m; ++i)
{
x = read();
b.push_back(x);
v.push_back(x);
}
sort(v.begin(), v.end(), cmp);
for(int i = 0; i < v.size() - 1; ++i)
if(v[i] != v[i + 1]) p.push_back(v[i]);
p.push_back(v[v.size() - 1]);
build();
// for(int x : p) cout << x <<" ";
// cout << "!!\n";
dij();
for(int x : p) g[x].clear();
}
}
/*
7
1 2
1 3
2 4
2 5
3 6
3 7
3
2 2
4 1
7 1
1 3
2 2
4 3
7 1
1 3
3 3
1 1
4 100
7 100
1 2 3
*/
本文来自博客园,作者:蒟蒻orz,转载请注明原文链接:https://www.cnblogs.com/orzz/p/18121985