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
",d[2]);             
    }
    return 0;
}