#include using namespace std; typedef long long LL; const int N = 100010, M = 300010; //与AcWing 1169. 糖果 这道题一模一样,连测试用例都一样 stack q; //有时候换成栈判断环很快就能 LL dist[N]; bool st[N]; int cnt[N]; int n, m; //表示点数和边数 //邻接表 int e[M], h[N], idx, w[M], ne[M]; void add(int a, int b, int c) { e[idx] = b, ne[idx] = h[a], w[idx] = c, h[a] = idx++; } bool spfa() { //求最长路,所以判断正环 memset(dist, -0x3f, sizeof dist); //初始化为-0x3f //差分约束从超级源点出发 dist[0] = 0; q.push(0); st[0] = true; while (q.size()) { int u = q.top(); q.pop(); st[u] = false; for (int i = h[u]; ~i; i = ne[i]) { int j = e[i]; if (dist[j] < dist[u] + w[i]) { //求最长路 dist[j] = dist[u] + w[i]; cnt[j] = cnt[u] + 1; //注意多加了超级源点到各各节点的边 if (cnt[j] >= n + 1) return false; if (!st[j]) { q.push(j); st[j] = true; } } } } return true; } int main() { memset(h, -1, sizeof h); scanf("%d %d", &n, &m); for (int i = 0; i < m; i++) { int op, a, b; // op为选择 scanf("%d %d %d", &op, &a, &b); if (op == 1) /** a == b => (a >= b , b >= a) */ add(a, b, 0), add(b, a, 0); else if (op == 2) /** b >= a + 1 */ add(a, b, 1); else if (op == 3) /** a >= b */ add(b, a, 0); else if (op == 4) /** a >= b + 1 */ add(b, a, 1); else /** b >= a */ add(a, b, 0); } /** xi >= x0 + 1 (每个小朋友都要至少一个糖果)*/ //将所有节点与超级源点x0相连 for (int i = 1; i <= n; ++i) add(0, i, 1); if (!spfa()) puts("-1"); else { LL res = 0; for (int i = 1; i <= n; ++i) res += dist[i]; printf("%lld\n", res); } return 0; }