HDU 2112 HDU Today

题解：最短路，注意是无向图，而且有起点和终点相同的情况……

#include <iostream>

#include <cstdio>

#include <cstring>

#include <utility>

#include <queue>

#include <map>

using namespace std;

const int N=20005;

const int INF=9999999;

typedef pair<int,int>seg;
map<string,int>mp;

priority_queue<seg,vector<seg>,greater<seg> >q;

int d[N],u[N],v[N],w[N],head[N],next[N],m,n,k,p,cnt,min;

string begin,end,s;

bool vis[N];

void build(){

    memset(head,-1,sizeof(head));

    for(int e=1;e<=m;e++){

        cin>>s;u[e]=mp[s]?mp[s]:(mp[s]=++cnt);

        cin>>s;v[e]=mp[s]?mp[s]:(mp[s]=++cnt);

        scanf("%d",&w[e]);

        u[e+m]=v[e]; v[e+m]=u[e]; w[e+m]=w[e];  

        next[e]=head[u[e]]; head[u[e]]=e;  

        next[e+m]=head[u[e+m]]; head[u[e+m]]=e+m; 

    }

}

int Dijkstra(int src){

    memset(vis,0,sizeof(vis));

    for(int i=0;i<=cnt;i++)d[i]=INF;

    d[src]=0;

    q.push(make_pair(d[src],src));

    while(!q.empty()){

        seg now=q.top(); q.pop();

        int x=now.second;

        if (vis[x]) continue; vis[x]=1;

        for(int e=head[x];e!=-1;e=next[e])

        if(d[v[e]]>d[x]+w[e]){

            d[v[e]]=d[x]+w[e];

            q.push(make_pair(d[v[e]],v[e]));

        }

    }

}

int main(){

    while(~scanf("%d",&m)){

        if(m==-1)break;

        mp.clear();

        cin>>begin>>end;

        mp[begin]=1;

        mp[end]=2;

        cnt=2; build();

        if(begin==end){puts("0");continue;}

        Dijkstra(1);   

        if (d[2]==INF) puts("-1");

        else printf("%d\n",d[2]);             

    }

    return 0;

}