BZOJ3732 （Kruskal重构树）

Kruskal重构树上\(x\)和\(v\)的\(lca\)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];

int head[N], cntEdge;

inline void add(int u, int v){

	e[++cntEdge] = (Edge){ head[u], v}, head[u] = cntEdge;

}

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;

				add(tot, p), add(tot, q);

//				add(p, tot), add(q, tot);

				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;

		add(u, v);

		add(v, u);

		printf("%d\n", val[TCP::LCA(u, v)]);

	}

	return 0;

}

BZOJ3732 （Kruskal重构树）的相关教程结束。