1874畅通工程续（dijkstra算法）

迷糊了好长时间，一开始有好多不理解的，到现在还没完全理清，不过比上午好多了，感觉不错，

#include<iostream>
#include<cstring>
#include<algorithm>
#include<queue>
using namespace std;
int n,m;
const int maxn = 210;
const int maxm = 2010;
const int inf = 0x3f3f3f3f;
typedef pair<int,int> pii;
int v[maxm],next[maxm],w[maxm];
int first[maxn],d[maxn],e;

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 dijkstra(int src)
{
    priority_queue<pii,vector<pii>,greater<pii> >q;
    memset(d,-1,sizeof(d));
    d[src] = 0;
    q.push(make_pair(0,src));
    while(!q.empty())
    {
        //while(!q.empty()/*&&q.top().first>d[q.top().second]*/)
            //q.pop();
        //if(q.empty())break;
        int u = q.top().second;
        q.pop();
        for(int i = first[u];i!=-1;i= next[i])
        {
            if(d[v[i]]==-1||d[v[i]]>d[u]+w[i])
            {
                d[v[i]] = d[u]+w[i];
                q.push(make_pair(d[v[i]],v[i]));
            }
        }
    }
}

int main()
{
    while(cin >> n>> m)
    {
        init();
        int a,b,c;
        for(int i =0;i < m;i++)
        {

            cin >> a>> b>> c;
            add_edge(a,b,c);
            add_edge(b,a,c);

        }
        int x,y;
        cin >> x>> y;
        dijkstra(x);
        if(d[y]!= inf)cout<< d[y]<< endl;
        else cout<< "-1"<< endl;
    }
    return 0;
}

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