Kruskal最小生成树

贪心+并查集

struct edge {
    int from, to, dist;
    bool operator < (const edge &ths) const {
        return dist < ths.dist;
    }
}e[N];

int find(int k) {
    return f[k] == k ? k : f[k] = find(f[k]);
}

int main() {
    int ans = 0;
    for(int i = 0; i < n; i++) scanf("%d%d%d", &e[i].from, &e[i].to, &e[i].dist);
    sort(e, e + n);
    for(int i = 0; i < n; i++) {
        if(find(e[i].from) != find(e[i].to)) {
            f[find(e[i].from)] = find(e[i].to);
            ans += e[i].dist;
        }
    }
}