【LOJ】#3087. 「GXOI / GZOI2019」旅行者

LOJ#3087. 「GXOI / GZOI2019」旅行者

正着求一遍dij，反着求一遍，然后枚举每条边，从u到v，如果到u最近的点和v能到的最近的点不同，那么可以更新答案

没了

#include <bits/stdc++.h>
#define fi first
#define se second
#define pii pair<int,int>
#define mp make_pair
#define pb push_back
#define space putchar(' ')
#define enter putchar('\n')
#define eps 1e-10
#define MAXN 100005
#define ba 47
//#define ivorysi
using namespace std;
typedef long long int64;
typedef unsigned int u32;
typedef double db;
template<class T>
void read(T &res) {
    res = 0;T f = 1;char c = getchar();
    while(c < '0' || c > '9') {
	if(c == '-') f = -1;
	c = getchar();
    }
    while(c >= '0' && c <= '9') {
	res = res * 10 +c - '0';
	c = getchar();
    }
    res *= f;
}
template<class T>
void out(T x) {
    if(x < 0) {x = -x;putchar('-');}
    if(x >= 10) {
	out(x / 10);
    }
    putchar('0' + x % 10);
}
struct node {
    int to,next;
    int64 val;
}E[500005];
int N,M,K;
int head[MAXN],sumE,u[500005],v[500005],c[500005];
vector<int> st;
int64 dis[2][MAXN],from[2][MAXN];
bool vis[MAXN];
void add(int u,int v,int64 c) {
    E[++sumE].to = v;
    E[sumE].next = head[u];
    E[sumE].val = c;
    head[u] = sumE;
}
void Init() {
    read(N);read(M);read(K);
    int a,b;
    for(int i = 1 ; i <= M ; ++i) {
	read(u[i]);read(v[i]);read(c[i]);
    }
    st.clear();
    for(int i = 1 ; i <= K ; ++i) {
	read(a);st.pb(a);
    }
}
priority_queue<pair<int64,int> > Q;
void Dijkstra(int id) {
    for(int i = 1 ; i <= N ; ++i) {
	dis[id][i] = 1e18;
    }
    for(auto t : st) {
	dis[id][t] = 0;from[id][t] = t;
	Q.push(mp(-dis[id][t],t));
    }
    memset(vis,0,sizeof(vis));
    while(!Q.empty()) {
	auto now = Q.top();Q.pop();
	if(vis[now.se]) continue;
	int t = now.se;
	vis[t] = 1;
	for(int i = head[t] ; i ; i = E[i].next) {
	    int v = E[i].to;
	    if(dis[id][v] > dis[id][t] + E[i].val) {
		dis[id][v] = dis[id][t] + E[i].val;
		from[id][v] = from[id][t];
		Q.push(mp(-dis[id][v],v));
	    }
	}
    }
}
void Solve() {
    sumE = 0;memset(head,0,sizeof(head));
    for(int i = 1 ; i <= M ; ++i) {
	add(u[i],v[i],c[i]);
    }
    
    Dijkstra(0);
    sumE = 0;memset(head,0,sizeof(head));
    for(int i = 1 ; i <= M ; ++i) {
	add(v[i],u[i],c[i]);
    }
    Dijkstra(1);
    int64 ans = 1e18;
    for(int i = 1 ; i <= M ; ++i) {
	if(from[0][u[i]] != from[1][v[i]]) {
	    ans = min(ans,c[i] + dis[0][u[i]] + dis[1][v[i]]);
	}
    }
    out(ans);enter;
}
int main() {
#ifdef ivorysi
    freopen("f1.in","r",stdin);
#endif
    int T;
    read(T);
    while(T--) {
	Init();
	Solve();
    }
}