BZOJ3732 （Kruskal重构树）

Kruskal重构树上$x$$v$$lca$的权值即为它们最长路最小值

#include <cstdio>
#include <iostream>
#include <cstring>
#include <algorithm>
#include <cmath>
#define R(a,b,c) for(register int a = (b); (a) <= (c); ++(a))
#define nR(a,b,c) for(register int a = (b); (a) >= (c); --(a))
#define Fill(a,b) memset(a, b, sizeof(a))
#define Swap(a,b) ((a) ^= (b) ^= (a) ^= (b))
#define ll long long
#define u32 unsigned int
#define u64 unsigned long long

#define ON_DEBUGG

#ifdef ON_DEBUGG

#define D_e_Line printf("\n----------\n")
#define D_e(x) cout << (#x) << " : " << x << endl
#define Pause() system("pause")
#define FileOpen() freopen("in.txt", "r", stdin)
#define FileSave() freopen("out.txt", "w", stdout)
#include <ctime>
#define TIME() fprintf(stderr, "\ntime: %.3fms\n", clock() * 1000.0 / CLOCKS_PER_SEC)

#else

#define D_e_Line ;
#define D_e(x) ;
#define Pause() ;
#define FileOpen() ;
#define FileSave() ;
#define TIME() ;
//char buf[1 << 21], *p1 = buf, *p2 = buf;
//#define getchar() (p1 == p2 && (p2 = (p1 = buf) + fread(buf, 1, 1 << 21, stdin), p1 == p2) ? EOF : *p1++)

#endif

using namespace std;
struct ios{
template<typename ATP>inline ios& operator >> (ATP &x){
x = 0; int f = 1; char ch;
for(ch = getchar(); ch < '0' || ch > '9'; ch = getchar()) if(ch == '-') f = -1;
while(ch >= '0' && ch <= '9') x = x * 10 + (ch ^ '0'), ch = getchar();
x *= f;
return *this;
}
}io;

template<typename ATP>inline ATP Max(ATP a, ATP b){
return a > b ? a : b;
}
template<typename ATP>inline ATP Min(ATP a, ATP b){
return a < b ? a : b;
}
template<typename ATP>inline ATP Abs(ATP a){
return a < 0 ? -a : a;
}

const int N = 30007;

struct Edge{
int nxt, pre;
}e[N << 2];
inline void add(int u, int v){
}
struct node{
int x, y, w;
bool operator < (const node &com) const{
return w < com.w;
}
}a[N << 1];

int n, m;
int val[N];
namespace KRUS{

int fa[N];
inline int Find(int x){
return x == fa[x] ? x : fa[x] = Find(fa[x]);
}
inline void Kruskal(){
sort(a + 1, a + m + 1);
int tot = n + 1, lim = n << 1;
R(i,1,lim) fa[i] = i;//, siz[i] = 1;
R(i,1,m){
int p = Find(a[i].x), q = Find(a[i].y);
if(p != q){
fa[p] = fa[q] = tot;
val[tot] = a[i].w;
if(++tot >= lim) break;
}
}
}

}
namespace TCP{
int fa[N], top[N], son[N], siz[N], dep[N];
inline void DFS_First(int u, int father){
fa[u] = father, siz[u] = 1, dep[u] = dep[father] + 1;
for(register int i = head[u]; i;i =  e[i].nxt){
int v = e[i].pre;
if(v == father) continue;
DFS_First(v, u);
siz[u] += siz[v];
if(siz[v] > siz[son[u]]) son[u] = v;
}
}
inline void DFS_Second(int u, int TP){
top[u] = TP;
if(!son[u]) return;
DFS_Second(son[u], TP);
for(register int i = head[u]; i; i = e[i].nxt){
int v = e[i].pre;
if(v != fa[u] && v !=  son[u])
DFS_Second(v, v);
}
}
inline int LCA(int x, int y){
while(top[x] != top[y]){
if(dep[top[x]] < dep[top[y]]) Swap(x, y);
x = fa[top[x]];
}
return dep[x] < dep[y] ? x : y;
}
}
int main(){
freopen("3732Network.in", "r", stdin);
freopen("3732Network.out", "w", stdout);
int Q;
io >> n >> m >> Q;
R(i,1,m){
io >> a[i].x >> a[i].y >> a[i].w;
}
KRUS::Kruskal();
int root = (n << 1) - 1; // root is 2 * n - 1
TCP::DFS_First(root, 0);
TCP::DFS_Second(root, root);
while(Q--){
int u, v;
io >> u >> v;