1160. Network 夜

http://acm.timus.ru/problem.aspx?space=1&num=1160

最短路变形  水题  spfa

代码：

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<string>
#include<vector>
#include<map>
#include<queue>
#include<stack>
#include<cmath>
#define LL long long
//#pragma comment(linker, "/STACK:1024000000,1024000000")
using namespace std;

const int INF=0x3f3f3f3f;
const int N=1005;
const int M=30005;
int head[N],I;
struct node
{
    int j,next,v;
}side[M];
int f[N];
void Add(int i,int j,int v)
{
    side[I].j=j;
    side[I].v=v;
    side[I].next=head[i];
    head[i]=I++;
}
int spfa(int s,int n)
{
    int dist[N];
    bool in[N];
    for(int i=1;i<=n;++i)
    dist[i]=INF;
    dist[1]=0;
    memset(in,false,sizeof(in));
    queue<int>qt;
    qt.push(s);
    in[s]=true;
    while(!qt.empty())
    {
        int x=qt.front();qt.pop();
        in[x]=false;
        for(int t=head[x];t!=-1;t=side[t].next)
        {
            int l=side[t].j;
            if(dist[l]>max(dist[x],side[t].v))
            {
                dist[l]=max(dist[x],side[t].v);
                f[l]=x;
                if(!in[l])
                {
                    in[l]=true;
                    qt.push(l);
                }
            }
        }
    }
    int k=0;
    for(int i=1;i<=n;++i)
    k=max(k,dist[i]);
    return k;
}
int main()
{
    //freopen("data.txt","r",stdin);
    int n,m;
    while(scanf("%d %d",&n,&m)!=EOF)
    {
        memset(head,-1,sizeof(head));
        I=0;
        while(m--)
        {
            int a,b,c;
            scanf("%d %d %d",&a,&b,&c);
            Add(a,b,c);
            Add(b,a,c);
        }
        printf("%d\n",spfa(1,n));
        printf("%d\n",n-1);
        for(int i=2;i<=n;++i)
        printf("%d %d\n",f[i],i);
    }
    return 0;
}