Implication Graph

INCLUDE
Graph::SCC ➝ /cp/graph/scc
Code

namespace Graph {
    template<int32_t N_> class ImplicationGraph {
        static_assert(N_ > 0, "N must be positive");
        static constexpr int32_t N = N_;

    private:
        Graph::SCC<N> scc;
        int n;
    
    public:
        ImplicationGraph() {}

        void set(int n_) { n = n_; scc.set(2 * n + 1); }

        void addClause(int u, int v) {
            // add both since implication graph is a kind of
            // skew-symmetric graph where x => y <=> ~y => ~x
            scc.addEdge(u, v);
            scc.addEdge(v ^ 1, u ^ 1);
        }

        vector<int> solve() {
            vector<int> solution(n + 1, -1);
            vector<vector<int>> components = scc.kosaraju();
            for (auto& co : components) {
                if (solution[co[0] >> 1] != -1) continue;
                for (auto& u : co) {
                    int x = u >> 1;
                    if (solution[x] != -1) return {};
                    solution[x] = u & 1;
                }
            }
            return solution;
        }
    };
}

constexpr int N = 1'000'005;
Graph::ImplicationGraph<N> ig;

inline void solve() {
    int n, m; cin >> n >> m;
    ig.set(n);
    for (int i = 0; i < m; ++i) {
        // input x => y
        int x, y; bool x_negated, y_negated;
        cin >> x >> x_negated >> y >> y_negated;
        ig.addClause((x << 1) | x_negated, (y << 1) | y_negated);
    }

    vector<int> solution = ig.solve();
    for (int i = 1; i <= n; ++i) {
        cout << solution[i] << ' ';
    }
    cout << endl;
}
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Code
