Poj 1135 domino effect

The most short-circuit problem, I use spfa.

Obtain the shortest time of each vertex.

Then the length of each edge is (d [u] + d [v] + Len)/2 Len.

Find the longest time.

#include<cstdio>#include<cstring>#include<algorithm>#include<queue>#include<vector>using namespace std;int n,m;struct lx{    int v;    double t;};vector<lx> g[501];double d[501];bool vis[501];void SPFA(){    for(int i=0;i<=n;i++)        d[i]=100000000.0,vis[i]=0;    queue<int>q;    d[1]=0,vis[1]=1,q.push(1);    while(!q.empty())    {        int u=q.front();q.pop();        vis[u]=0;        for(int j=0;j<g[u].size();j++)        {            int v=g[u][j].v;            double t=g[u][j].t;            if(d[v]>d[u]+t)            {                d[v]=d[u]+t;                if(!vis[v])                {                    vis[v]=1;                    q.push(v);                }            }        }    }    int p,p1,p2;    double t, t1=-100001.0,t2=-100001.0;    for(int i=1;i<=n;i++)    {        for(int j=0;j<g[i].size();j++)        {            t=(d[i]+d[g[i][j].v]+g[i][j].t)/2;            if(t>t2)                p1=i,p2=g[i][j].v,t2=t;        }    }    for(int i=1;i<=n;i++)        if(d[i]>t1)t1=d[i],p=i;    if(t1>=t2)    {        printf("The last domino falls after %.1f seconds, at key domino %d.\n",t1,p);    }    else    {         printf("The last domino falls after %.1f seconds, between key dominoes %d and %d.\n",t2,p1,p2);    }}int main(){    int cot=1;    while(scanf("%d%d",&n,&m)!=EOF)    {        if(n==0&&m==0)return 0;        for(int i=0;i<=n;i++)            g[i].clear();        for(int i=0;i<m;i++)        {            int u,v;            lx now;            scanf("%d%d%lf",&u,&v,&now.t);            now.v=v;            g[u].push_back(now);            now.v=u;            g[v].push_back(now);        }        printf("System #%d\n",cot++);        SPFA();        printf("\n");    }    return 0;}