抠了一天的最短路问题，那个spfa还真是难写，只能照着模板打一遍，还有那个松弛操作有点明白怎么回事，但还是不太清晰，容我再抠抠，然后再用dijksta算法敲一遍这道题吧!

#include
     
      #include
      
       #include
       
        #include
        
         int n,m;const int inf = 0x3f3f3f3f;int v[2010],next[2010],w[2010];int first[210],d[210],inq[210],e;using namespace std;void init(){    e = 0;    memset(first,-1,sizeof(first));}void add_edge(int a,int b,int c){    v[e] = b;    next[e] = first[a];    w[e]= c;    first[a] = e++;}void spfa(int src){    queue
         
           q;    memset(d,0x3f,sizeof(d));    d[src] = 0,inq[src] = 1;    q.push(src);    while(!q.empty()){        int u = q.front();        q.pop();        inq[u] = 0;        for(int i = first[u];i != -1;i = next[i]){            if(d[v[i]] > d[u]+w[i]){                d[v[i]] = d[u]+w[i];                if(!inq[v[i]])  q.push(v[i]),inq[v[i]] = 1;            }        }    }}int main(){    while(cin >> n>>m)    {        init();        for(int i =0;i < m;i++)        {            int a,b,c;            cin >> a>> b>> c;            add_edge(a,b,c);            add_edge(b,a,c);        }        int x,y;        cin >> x>> y;        spfa(x);        if(d[y] != inf)cout<< d[y]<< endl;        else cout<< "-1"<< endl;    }    return 0;}