用add加边, 最后调用solve返回一个vector<int>, 为空则无解, 否则为一组解.

struct TWO_SAT {
    int siz;
    std::vector<std::vector<int>> gra;
    TWO_SAT(int size) : siz(size), gra(siz * 2 + 1) {}
    // i -> x_i == 0, i + n -> x_i == 1
    void add(int a, bool ta, int b, bool tb) {
        gra[a + !ta * siz].push_back(b + tb * siz);
        gra[b + !tb * siz].push_back(a + ta * siz);
    }

    std::vector<int> solve() {
        std::vector<int> low(siz * 2 + 1), scc(siz * 2 + 1);
        std::stack<int> sta;
        int idx = 1, cnt = 0;
        auto dfs = [&](int u, auto self) -> void {
            low[u] = idx++;
            int now = low[u];
            sta.push(u);
            for (auto v : gra[u]) {
                if (!low[v])
                    self(v, self), low[u] = min(low[u], low[v]);
                else if (!scc[v])
                    low[u] = min(low[u], low[v]);
            }
            if (low[sta.top()] >= now) {
                cnt++;
                while (sta.size() && low[sta.top()] >= now) {
                    auto t = sta.top();
                    sta.pop();
                    scc[t] = cnt;
                }
            }
        };
        for (int i = 1; i <= 2 * siz; i++) {
            if (!low[i])
                dfs(i, dfs);
        }
        std::vector<int> ans(siz + 1);
        for (int i = 1; i <= siz; i++) {
            if (scc[i] == scc[i + siz]) {
                return std::vector<int>();
            }
            ans[i] = scc[i] > scc[i + siz];
        }
        return ans;
    }
};

exp: P4782 【模板】2-SAT

void solve() {
    int n, m;
    cin >> n >> m;
    TWO_SAT ts(n);
    for (int i = 0; i < m; i++) {
        int a, b, c, d;
        cin >> a >> b >> c >> d;
        ts.add(a, b, c, d);
    }
    auto res = ts.solve();
    if (res.empty()) {
        cout << "IMPOSSIBLE\n";
    } else {
        cout << "POSSIBLE\n";
        for (int i = 1; i <= n; i++) {
            cout << res[i] << ' ';
        }
        cout << '\n';
    }
}