[Explanations] luogu p1111 road repairs

to sum up:

1. disjoint-set master board unskilled

#include<bits/stdc++.h>
using namespace std;
int n, m, fa[1005], t, sum[1005];
struct node{
    int u, v, t;
}a[100005];

bool cmp(node x, node y)
{
    return x.t < y.t;
}

int find(int x)
{
    if(fa[x] == x) return x;
    else return fa[x] = find(fa[x]);
}

void hb(int x, int y, int z)
{
    if(find(x) != find(y))
    {
        fa[find(x)] = find(y);
        sum[find(y)] += sum[find(x)];
    } 
    if(sum[find(y)] == n)
    {
        cout << a[z].t;
        exit(0);
    }
}

int main()
{
    cin >> n >> m;
    for(int i = 1; i <= m; i++)
        cin >> a[i].u >> a[i].v >> a[i].t;
    sort(a+1, a+1+m, cmp);
    for(int i = 1; i <= n; i++)
        fa[i] = i, sum[i] = 1;
    for(int i = 1; i <= m; i++)
        hb(a[i].u, a[i].v, i);
    cout << "-1";
    return 0;
}