百练1511:Invitation Cards题解

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1511:Invitation Cards

题目链接：点击打开链接

代码：

#include<cstdio>#include<queue>#include<cstring>#include<vector>using namespace std;typedef long long ll;const int N = 1000005;typedef pair<int, int > PAIR;struct Edge{    int to;    int price;    int next;};Edge G[N],rG[N];int head1[N],head2[N];ll dis[N];void spfa(){    memset(dis,0x3f,sizeof(dis));    priority_queue<PAIR, vector<PAIR>, greater<PAIR> > que;    que.push(PAIR(0,1)); dis[1] = 0;    while(!que.empty()){        int u = que.top().second;        que.pop();        for(int i = head1[u];i; i = G[i].next){            Edge e = G[i];            if(dis[e.to] > dis[u] + e.price){                dis[e.to] = dis[u] + e.price;                que.emplace(dis[e.to],e.to);            }        }    }}void spfa2(){    memset(dis,0x3f,sizeof(dis));    priority_queue<PAIR, vector<PAIR>, greater<PAIR> > que;    que.push(PAIR(0,1)); dis[1] = 0;    while(!que.empty()){        int u = que.top().second;        que.pop();        for(int i = head2[u];i; i = rG[i].next){            Edge e = rG[i];            if(dis[e.to] > dis[u] + e.price){                dis[e.to] = dis[u] + e.price;                que.emplace(dis[e.to],e.to);            }        }    }}int main(){    int n,p,q;    scanf("%d",&n);    while(n--){        memset(head1,0,sizeof(head1));        memset(head2,0,sizeof(head2));        scanf("%d%d",&p,&q);        for(int i = 1; i <= q; ++i){            int from,to,price;            scanf("%d%d%d",&from,&to,&price);            Edge e = {to,price,0};            G[i] = e;            G[i].next = head1[from];            head1[from] = i;            e.to = from;            rG[i] = e;            rG[i].next = head2[to];            head2[to] = i;        }        ll ans = 0;        spfa();        for(int i = 2; i <= p; ++i) ans += dis[i];        spfa2();        for(int i = 2; i <= p; ++i) ans += dis[i];        printf("%lld\n", ans);    }    return 0;}

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