loj2182 「SDOI2015」寻宝游戏

参考这里

#include <iostream>
#include <cstdio>
#include <set>
using namespace std;
typedef long long ll;
int n, m, ise[100005], fa[100005][19], dep[100005], uu, vv, ww, hea[100005], cnt;
int faq, nfd[100005];
ll dis[100005], ans;
struct Edge{
	int too, nxt, val;
}edge[200005];
struct Node{
	int idx, dfn;
	bool operator<(const Node &x)const{
		return dfn<x.dfn;
	}
};
set<Node> qwq;
void add_edge(int fro, int too, int val){
	edge[++cnt].nxt = hea[fro];
	edge[cnt].too = too;
	edge[cnt].val = val;
	hea[fro] = cnt;
}
void dfs(int x, int f, ll d){
	nfd[x] = ++faq;
	dis[x] = d;
	fa[x][0] = f;
	dep[x] = dep[f] + 1;
	for(int i=hea[x]; i; i=edge[i].nxt){
		int t=edge[i].too;
		if(t!=f)	dfs(t, x, d+edge[i].val);
	}
}
int queryPre(int x){
	set<Node>::iterator i=qwq.lower_bound((Node){x, nfd[x]});
	if(i==qwq.begin())	i = qwq.end();
	return (*(--i)).idx;
}
int queryNxt(int x){
	set<Node>::iterator i=qwq.lower_bound((Node){x, nfd[x]});
	if((++i)==qwq.end())	i = qwq.begin();
	return (*i).idx;
}
int lca(int x, int y){
	if(dep[x]<dep[y])	swap(x, y);
	for(int i=16; i>=0; i--)
		if(dep[fa[x][i]]>=dep[y])
			x = fa[x][i];
	if(x==y)	return x;
	for(int i=16; i>=0; i--)
		if(fa[x][i]!=fa[y][i]){
			x = fa[x][i];
			y = fa[y][i];
		}
	return fa[x][0];
}
ll qdis(int x, int y){
	return dis[x]+dis[y]-2*dis[lca(x, y)];
}
ll query(int x){
	int pre, nxt, fla;
	if(!ise[x]){
		fla = 1;
		qwq.insert((Node){x, nfd[x]});
		pre = queryPre(x);
		nxt = queryNxt(x);
	}
	else{
		fla = -1;
		pre = queryPre(x);
		nxt = queryNxt(x);
		qwq.erase((Node){x, nfd[x]});
	}
	ise[x] ^= 1;
	if(qwq.size()<=1)	ans = 0;
	else	ans += fla * (qdis(pre, x)+qdis(x, nxt)-qdis(pre, nxt));
	return ans;
}
int main(){
	cin>>n>>m;
	for(int i=1; i<n; i++){
		scanf("%d %d %d", &uu, &vv, &ww);
		add_edge(uu, vv, ww);
		add_edge(vv, uu, ww);
	}
	dfs(1, 0, 0);
	for(int i=1; i<=16; i++)
		for(int j=1; j<=n; j++)
			fa[j][i] = fa[fa[j][i-1]][i-1];
	while(m--){
		scanf("%d", &uu);
		printf("%lld\n", query(uu));
	}
	return 0;
}