局域网(最小生成树思维题)

题目链接
思路：根据题意要使得图中不成环，那么删去边后剩下的图肯定就是一棵树，又因为要使得删去边的权值总和最大，就意味着剩下那棵树的权值总和要尽量小，毫无疑问剩下那棵树就是这幅图的最小生成树，所以直接求最小生成树就行了。
ac代码：

#include 
#include 
#include 
#include 
#include 
#include 
using namespace std;
#define int long long
int head[105];
struct node {
	int st, ed, val;
};
vector<node> ll;
bool cmp(node a, node b) {
	return a.val < b.val;
}
int f(int a) {
	if (head[a] == 0) return a;
	else return head[a] = f(head[a]);
}
signed main() {
	ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
	int n, m; cin >> n >> m; int sum = 0;
	for (int i = 0; i < m; i++) {
		node q; int u, v, w; cin >> u >> v >> w;
		q.st = u, q.ed = v, q.val = w; sum += w;
		ll.push_back(q);
	}
	sort(ll.begin(), ll.end(), cmp);
	int ret = 0;
	for (int i = 0; i < m; i++) {
		node g = ll[i];
		if (f(g.st) != f(g.ed)) {
			head[f(g.ed)] = f(g.st);
			ret += g.val;
		}
	}
	cout << sum - ret << endl;
	return 0;
}