[NOIP 2010] 关押罪犯

#include<bits/stdc++.h>
using namespace std;
#define MAXN 20010
#define MAXM 100010

struct info
{
    int u,v,w;
} a[MAXM];

int i,n,m;
int fa[MAXN<<1];

inline bool cmp(info a,info b)
{
    return a.w > b.w;
}
inline int get_root(int x)
{
    if (fa[x] == x) return x;
    return fa[x] = get_root(fa[x]);    
}

int main()
{

    scanf("%d%d",&n,&m);
    for (i = 1; i <= m; i++) scanf("%d%d%d",&a[i].u,&a[i].v,&a[i].w);
    sort(a+1,a+m+1,cmp);
    for (i = 1; i <= 2 * n; i++) fa[i] = i;
    for (i = 1; i <= m; i++)
    {
        if (get_root(a[i].u) == get_root(a[i].v))
        {
            printf("%d\n",a[i].w);
            return 0; 
        } else
        {
            fa[get_root(a[i].u)] = get_root(a[i].v+n);
            fa[get_root(a[i].v)] = get_root(a[i].u+n);
        }
    }
    printf("0\n");

    return 0;
}