差分约束

#include <bits/stdc++.h>
using namespace std;
const int N = 1e5 + 10, M = 3e5 + 10;
int h[N], e[M], ne[M], w[M], idx;
bool st[N];
int cnt[N];
long long int dist[N];
int n, m;
void add(int a, int b, int c)
{
    e[idx] = b, w[idx] = c, ne[idx] = h[a], h[a] = idx ++;
}

bool spfa()
{
    int q[N], hh = -1, tt = 0;
    memset(dist, -0x3f,sizeof dist);
    q[0] = 0;
    st[0] = true;
    dist[0] = 0;

    while (hh != tt)
    {
        int t = q[tt --];
        st[t] = false;
        for (int i = h[t]; ~i; i = ne[i])
        {
            int j = e[i];
            if (dist[j] < dist[t] + w[i])
            {
                dist[j] = dist[t] + w[i];
                cnt[j] = cnt[t] + 1;
                if (cnt[j] >= n + 1) return true;
                if (!st[j])
                {
                    q[++ tt] = j;
                    st[j] = true;
                }
            }
        }
    }
    return false;
}

int main(void)
{
    memset(h, -1, sizeof h);
    cin >> n >> m;

    for (int i = 0; i < m; i ++)
    {
        int x, a, b;
        cin >> x >> a >> b;
        if (x == 1) add(a, b, 0), add(b, a, 0);
        else if (x == 2) add(a, b, 1);
        else if (x == 3) add(b, a, 0);
        else if (x == 4) add(b, a, 1);
        else if (x == 5) add(a, b, 0);
    }

    for (int i = 1; i <= n; i ++) add(0, i, 1);

    if (spfa()) puts("-1");
    else
    {
        long long int res = 0;
        for (int i = 1; i <= n; i ++) res += dist[i];
        printf("%lld\n", res);
    }
    return 0;
}