kruskal

struct node {
    int u, v, w;

    bool operator<(const node &b) const {
        return w < b.w;
    }
}a[M];

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

void union1(int x,int y) {
    f[x] = y;
}

int main() {
    scanf("%d%d", &n, &m);
    for (int i = 1; i <= n; i++) {
        f[i] = i;
    }
    for (int i = 1; i <= m; i++) {
        scanf("%d%d%d", &a[i].u, &a[i].v, &a[i].w);
    }
    sort(a + 1, a + m + 1);
    for (int i = 1; i <= m; i++) {
        int x = find(a[i].u), y = find(a[i].v);
        if (x != y) {
            union1(x, y);
            k++;
            ans += a[i].w;
        }
        if (k == n - 1) {
            break;
        }
    }
    printf("%d
", ans);
}