diff --git a/graph/tarjan.cc b/graph/tarjan.cc
index 715accd..77c5612 100644
--- a/graph/tarjan.cc
+++ b/graph/tarjan.cc
@@ -1,4 +1,14 @@
 namespace tarjan {
+    struct mutex_cond {
+        int v1; bool cond1;
+        int v2; bool cond2;
+        mutex_cond(int v1, bool cond1, int v2, bool cond2) : v1(v1), cond1(cond1), v2(v2), cond2(cond2) {}
+    };
+    struct inclusive_cond {
+        int v1; bool cond1;
+        int v2; bool cond2;
+        inclusive_cond(int v1, bool cond1, int v2, bool cond2) : v1(v1), cond1(cond1), v2(v2), cond2(cond2) {}
+    };
     // Returns the mapping between vertices and their affiliated sccs.
     vector<int> scc(const vector<vector<int>>& ch) {
         int n = ch.size();
@@ -25,7 +35,6 @@ namespace tarjan {
         }
         return br;
     }
-
     // This method can eliminate redundant edges or self-loops
     vector<vector<int>> build_scc(const vector<vector<int>>& ch) {
         int n = ch.size();
@@ -65,4 +74,35 @@ namespace tarjan {
         }
         return res;
     }
+    // indices start from 1, result has `n` items
+    optional<vector<bool>> solve_twosat(int n, const vector<mutex_cond>& conditions) {
+        vector<vector<int>> ch(2 * n + 1);
+        for (auto&& [v1, cond1, v2, cond2] : conditions) {
+            ch[(1 ^ cond1) * n + v1].emplace_back(cond2 * n + v2);
+            ch[(1 ^ cond2) * n + v2].emplace_back(cond1 * n + v1);
+        }
+        auto sccno = scc(ch);
+        for (int i = 1; i <= n; ++i) {
+            if (sccno[i] == sccno[i + n]) {
+                return nullopt;
+            }
+        }
+        vector<bool> res;
+        for (int i = 1; i <= n; ++i) {
+            if (sccno[i] < sccno[i + n]) {
+                res.emplace_back(false);
+            } else {
+                res.emplace_back(true);
+            }
+        }
+        return res;
+    };
+    // indices start from 1, result has `n` items
+    optional<vector<bool>> solve_twosat(int n, const vector<inclusive_cond>& conditions) {
+        vector<mutex_cond> trans_conds;
+        for (auto&& [v1, cond1, v2, cond2] : conditions) {
+            trans_conds.emplace_back(v1, cond1, v2, not cond2);
+        }
+        return solve_twosat(n, trans_conds);
+    }
 }