牛客国庆集训派对Day3 I Metropolis

时间：2022-11-13 20:27:58

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 + ;

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 = ; i <= n; i++) d[i].fi = INF, d[i].se = , dis[i] = INF;

    for (int i = ; i < p; i++) scanf("%d", &u), d[u] = pii{, u}, q.push(piii{{, u}, u}), st.pb(u);

    for (int i = ; 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 ;

}

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