hdu1874畅通工程再续

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<iostream>
#include<cstring>
#include<algorithm>
#include<queue>
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<int> 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;
}