hdu-4738（tarjan割边）

#include<iostream>
#include<algorithm>
#include<cstdio>
#include<cstring>
#define maxn 1100
#define inf 0x3f3f3f3f
using namespace std;
struct Edge
{
    int next;
    int to;
    int w;
}edge[maxn*maxn*2];
int head[maxn*maxn];
int low[maxn*maxn];
int dfn[maxn*maxn];
int n,m;
int flag;
int minn;
int cnt,step;
int bridge;
void init()
{
    memset(head,-1,sizeof(head));
    memset(low,0,sizeof(low));
    memset(dfn,0,sizeof(dfn));
    cnt=0;step=0;bridge=0;flag=0;minn=inf;
}
void add(int u,int v,int w)
{
    edge[cnt].next=head[u];
    edge[cnt].to=v;
    edge[cnt].w=w;
    head[u]=cnt++;
}
void tarjan(int u,int fa)
{
    dfn[u]=low[u]=++step;
    int num=0;
    for(int i=head[u];i!=-1;i=edge[i].next)
    {
        int v=edge[i].to;
        if(fa==v&&num==0)
        {
            num++;
            continue;
        }
       // cout<<v<<endl;
        if(!dfn[v])
        {
            tarjan(v,u);
            low[u]=min(low[u],low[v]);
            if(low[v]>dfn[u])
            {
                bridge++;
                minn=min(minn,edge[i].w);
            }
        }
        else
            low[u]=min(low[u],dfn[v]);
    }
}
void solve()
{
    int ans=0;
    for(int i=1;i<=n;i++)
    {
        if(!dfn[i])
        {
            ans++;
            tarjan(i,i);
        }
    }
    if(ans>=2)
    {
        printf("0\n");
        return;
    }
    if(bridge==0)
        printf("-1\n");
    else
    {
        if(minn==0)
            printf("1\n");
        else
        printf("%d\n",minn);
    }
}
int main()
{
    int x,y,w;
    while(scanf("%d%d",&n,&m)!=EOF)
    {
        init();
        if(n==0&&m==0)
            break;
        for(int i=1;i<=m;i++)
        {
            scanf("%d%d%d",&x,&y,&w);
            add(x,y,w);
            add(y,x,w);
        }
        solve();
    }
    return 0;
}