P4017 最大食物链计数

// Problem: P4017 最大食物链计数
// Contest: Luogu
// URL: https://www.luogu.com.cn/problem/P4017
// Memory Limit: 125 MB
// Time Limit: 1000 ms
// User: Pannnn

#include 

using namespace std;

template
void debugVector(const T &a) {
    cout << "[ ";
    for (size_t i = 0; i < a.size(); ++i) {
        cout << a[i] << (i == a.size() - 1 ? " " : ", ");
    }
    cout << "]" << endl;
}

template
void debugVectorPair(const vector> &a) {
    cout << "{";
    for (size_t i = 0; i < a.size(); ++i) {
        cout << "[ " << a[i].first << ": " << a[i].second << (i == a.size() - 1 ? " ]" : " ], ");
    }
    cout << "}" << endl;
}


template
void debugMatrix2(const T &a) {
    for (size_t i = 0; i < a.size(); ++i) {
        debugVector(a[i]);
    }
}

template
using matrix2 = vector>;

template
vector> getMatrix2(size_t n, size_t m, T init = T()) {
    return vector>(n, vector(m, init));
}

template
using matrix3 = vector>>;

template
vector>> getMatrix3(size_t x, size_t y, size_t z, T init = T()) {
    return vector>>(x, vector>(y, vector(z, init)));
}

vector genBigInteger(const string &a) {
    vector res;
    if (a.empty()) return res;
    for (int i = a.size() - 1; i >= 0; --i) {
        res.push_back(a[i] - '0');
    }
    return res;
}

ostream &printBigInteger(const vector &a) {
    if (a.empty()) return cout;
    for (int i = a.size() - 1; i >= 0; --i) {
        cout << a[i];
    }
    return cout;
}

vector maxBigInteger(const vector &a, const vector &b) {
    if (a.size() > b.size()) {
        return a;
    } else if (a.size() < b.size()) {
        return b;
    }
    for (int i = a.size() - 1; i >= 0; --i) {
        if (a[i] > b[i]) {
            return a;
        } else if (a[i] < b[i]) {
            return b;
        }
    }
    return a;
}

vector addBigInteger(const vector &a, const vector &b) {
    vector res;
    int pre = 0;
    for (size_t i = 0; i < a.size() || i < b.size() || pre; ++i) {
        if (i < a.size()) pre += a[i];
        if (i < b.size()) pre += b[i];
        res.push_back(pre % 10);
        pre /= 10;
    }
    while (res.size() > 1 && res.back() == 0) {
        res.pop_back();
    }
    return res;
}

vector mulBigInteger(const vector &a, int b) {
    vector res;
    int pre = 0;
    for (size_t i = 0; i < a.size() || pre; ++i) {
        if (i < a.size()) pre += a[i] * b;
        res.push_back(pre % 10);
        pre /= 10;
    }
    while (res.size() > 1 && res.back() == 0) {
        res.pop_back();
    }
    return res;
}

vector divBigInteger(const vector &a, int b, int &r) {
    vector res;
    for (int i = a.size() - 1; i >= 0; --i) {
        r = 10 * r + a[i];
        res.push_back(r / b);
        r %= b;
    }
    reverse(res.begin(), res.end());
    while (res.size() > 1 && res.back() == 0) {
        res.pop_back();
    }
    return res;
}

vector getQue(int n, vector inDegree, matrix2 &path) {
    vector que;
    for (int i = 1; i <= n; ++i) {
        if (inDegree[i] == 0) {
            que.push_back(i);
        }
    }
    
    for (int i = 0; i < que.size(); ++i) {
        for (int j = 0; j < path[que[i]].size(); ++j) {
            --inDegree[path[que[i]][j]];
            if (inDegree[path[que[i]][j]] == 0) {
                que.push_back(path[que[i]][j]);
            }
        }
    }
    return que;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    
    int n, m;
    cin >> n >> m;
    matrix2 path = getMatrix2(n + 1, 0, 0);
    
    vector inDegree(n + 1);
    vector outDegree(n + 1);
    int a, b;
    for (int i = 0; i < m; ++i) {
        cin >> a >> b;
        path[a].push_back(b);
        ++inDegree[b];
        ++outDegree[a];
    }
    
    vector que = getQue(n, inDegree, path);
    // res[i] 以生产者开始，以i结尾的食物链条数
    vector res(n + 1);
    
    for (int i = 1; i <= n; ++i) {
        if (inDegree[i] == 0) {
            res[i] = 1;
        }
    }
    for (int i = 0; i < que.size(); ++i) {
        for (int j = 0; j < path[que[i]].size(); ++j) {
            res[path[que[i]][j]] += res[que[i]];
            res[path[que[i]][j]] %= 80112002;
        }
    }
    
    int cnt = 0;
    for (int i = 1; i <= n; ++i) {
        if (outDegree[i] == 0) {
            cnt += res[i];
            cnt %= 80112002;
        }
    }
    cout << cnt << endl;
    return 0;
}