POJ--3268 Silver Cow Party（最短路）

题目电波：POJ--3268 Silver Cow Party

跑两遍 dijkstra 就好了弱智题

#include<iostream>
#include<stdio.h>
#include<algorithm>
#include<queue>
#include<cstring>
using namespace std;
#define maxn 10001
#define inf 0x3f3f3f
#define pii pair<int,int>
struct ac{int to,va;ac(){}ac(int a,int b){to=a,va=b;}
};
vector<ac>q[maxn],w[maxn];
int dis[maxn],dist[maxn];
bool fa[maxn];
void dijkstra(int s){memset(fa,0,sizeof(fa));memset(dis,inf,sizeof(dis));priority_queue<pii,vector<pii>,greater<pii> >pq;dis[s]=0;pq.push(pii(dis[s],s));while(!pq.empty()){int u=pq.top().second;pq.pop();// cout<<"1"<<endl;if(fa[u]) continue;fa[u]=1;for(int j=0;j<q[u].size();j++){ac x=q[u][j];int v=x.to,va=x.va;if(dis[v]>dis[u]+va){dis[v]=dis[u]+va;pq.push(pii(dis[v],v));}}}
}
void dijkstra1(int s){memset(fa,0,sizeof(fa));memset(dist,inf,sizeof(dist));priority_queue<pii,vector<pii>,greater<pii> >pq;dist[s]=0;pq.push(pii(dist[s],s));while(!pq.empty()){//cout<<"2"<<endl;int u=pq.top().second;pq.pop();if(fa[u]) continue;fa[u]=1;for(int j=0;j<w[u].size();j++){ac x=w[u][j];int v=x.to,va=x.va;if(dist[v]>dist[u]+va){dist[v]=dist[u]+va;pq.push(pii(dist[v],v));}}}
}
int main(){int n,m,s;cin>>n>>m>>s;for(int j=0;j<m;j++){int u,v,va;scanf("%d%d%d",&u,&v,&va);q[u].push_back(ac(v,va));w[v].push_back(ac(u,va));}dijkstra(s);dijkstra1(s);int ans=0;for(int j=1;j<=n;j++){if(j==s) continue;ans=max(dis[j]+dist[j],ans);//cout<<dis[j]<<" "<<dist[j]<<endl;
   }cout<<ans<<endl;
}

转载于:https://www.cnblogs.com/DyLoder/p/9827684.html

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