牛客国庆集训派对Day3 I Metropolis

Metropolis

思路:

多源点最短路

只要两个不同源点的最短路相遇，我们就更新两个源点的答案

代码：

#pragma GCC optimize(2)
#pragma GCC optimize(3)
#pragma GCC optimize(4)
#include<bits/stdc++.h>
using namespace std;
#define fi first
#define se second
#define pi acos(-1.0)
#define LL long long
//#define mp make_pair
#define pb push_back
#define ls rt<<1, l, m
#define rs rt<<1|1, m+1, r
#define ULL unsigned LL
#define pll pair<LL, LL>
#define pli pair<LL, int>
#define pii pair<int, int>
#define piii pair<pli, int>
#define mem(a, b) memset(a, b, sizeof(a))
#define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
#define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout);
//head

const int N = 2e5 + 100;
const LL INF = 0x7f7f7f7f7f7f7f7f;
vector<pii> g[N];
priority_queue<piii, vector<piii>, greater<piii> > q;
pli d[N];
LL dis[N];
vector<int> st;
void dijkstra() {
    while(!q.empty()) {
        piii now = q.top();
        q.pop();
        int u = now.fi.se;
        if(d[u].fi < now.fi.fi) continue;
        for (pii t : g[u]) {
            int v = t.fi;
            int w = t.se;
            if(d[v].fi > w + now.fi.fi) {
                    d[v].se = now.se;
                    d[v].fi = w + now.fi.fi;
                    q.push(piii{{d[v].fi, v}, now.se});
            }
            if(d[v].se && d[v].se != now.se) {
                int u1 = d[v].se;
                int u2 = now.se;
                dis[u1] = min(dis[u1], d[v].fi+now.fi.fi + w);
                dis[u2] = min(dis[u2], d[v].fi+now.fi.fi + w);
            }
        }
    }
}
int main() {
    int n, m, p, u, v, w;
    scanf("%d %d %d", &n, &m, &p);
    for (int i = 1; i <= n; i++) d[i].fi = INF, d[i].se = 0, dis[i] = INF;
    for (int i = 0; i < p; i++) scanf("%d", &u), d[u] = pii{0, u}, q.push(piii{{0, u}, u}), st.pb(u);
    for (int i = 0; i < m; i++) {
        scanf("%d %d %d", &u, &v, &w);
        g[u].pb(pii{v, w});
        g[v].pb(pii{u, w});
    }
    dijkstra();
    for (int x : st) printf("%lld ", dis[x]);
    return 0;
}