【并查集】关押罪犯

#include <bits/stdc++.h>

using namespace std;
const int maxn=20010;
const int maxm=100010;

struct node {
    int x,y,w;
    bool operator<(const node &b)const {
        return w>b.w;
    }
}a[maxm];

int f[maxn*2];
int n,m;

int getfa(int x) {
    return x == f[x] ? x : f[x] = getfa(f[x]);
}
void merge(int x,int y) {
    int xx = getfa(x), yy = getfa(y);
    if (xx != yy) f[xx] = y;
}
int main() {
    scanf("%d%d", &n, &m);
    for (int i = 1; i <= n * 2; i++) {
        f[i] = i;
    }
    for (int i = 1; i <= m; i++) {
        scanf("%d%d%d", &a[i].x, &a[i].y, &a[i].w);
    }
    sort(a + 1, a + 1 + m);
    for (int i = 1; i <= m; i++) {
        if (getfa(a[i].x) == getfa(a[i].y)) {
            printf("%d\n", a[i].w);
            return 0;
        }
        merge(a[i].x + n, a[i].y);
        merge(a[i].y + n, a[i].x);
    }
    printf("0\n");
}