From 67d6efb9dda9d926730df4ea625def1e8c43b234 Mon Sep 17 00:00:00 2001
From: Connor De Meyer <connordemeyer@gmail.com>
Date: Mon, 25 Aug 2025 07:35:38 +0900
Subject: [PATCH] branch bug fix

---
 include/nd-wfc/wfc.hpp | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/include/nd-wfc/wfc.hpp b/include/nd-wfc/wfc.hpp
index 9136c1c..bd525c7 100644
--- a/include/nd-wfc/wfc.hpp
+++ b/include/nd-wfc/wfc.hpp
@@ -212,12 +212,12 @@ public:
 
 private:
     void ApplyMask(size_t cellId, MaskType mask) {
-        if (m_wave.IsCollapsed(cellId)) return;
+        bool wasCollapsed = m_wave.IsCollapsed(cellId);
 
         m_wave.Collapse(cellId, mask);
-        assert(!m_wave.HasContradiction() && "Contradiction found");
 
-        if (m_wave.IsCollapsed(cellId)) {
+        bool collapsed = m_wave.IsCollapsed(cellId);
+        if (!wasCollapsed && collapsed) {
             m_propagationQueue.push(cellId);
         }
     }
@@ -277,7 +277,7 @@ public:
     bool Run(WorldT& world, bool propagateInitialValues = false)
     {
         //auto seed = std::random_device{}();
-        auto seed = 1844803044ull;
+        auto seed = 1844803044ul;
         std::mt19937 random{ seed };
         SolverState state(world, m_variables.size(), random);
         return Run(state, propagateInitialValues);
@@ -307,12 +307,11 @@ public:
         constexpr size_t maxIterations = 1024;
         for (size_t i = 0; i < maxIterations; ++i)
         {
-            Propagate(state);
+            if (!Propagate(state))
+                return false;
 
             if (state.wave.IsFullyCollapsed()) {
                 return true;
-            } else if (state.wave.HasContradiction()) {
-                return false;
             } else {
                 Branch(state);
             }
@@ -414,19 +413,22 @@ private:
         return false;
     }
 
-    void Propagate(SolverState& state)
+    bool Propagate(SolverState& state)
     {
         while (!state.propagationQueue.empty())
         {
             size_t cellId = state.propagationQueue.front();
             state.propagationQueue.pop();
 
+            if (state.wave.IsContradicted(cellId)) return false;
+
             assert(state.wave.IsCollapsed(cellId) && "Cell was not collapsed");
 
             uint16_t variableID = state.wave.GetVariableID(cellId);
             Constrainer<VariableIDMapT> constrainer(state.wave, state.propagationQueue);
             m_variables[variableID].constraintFunc(state.world, cellId, WorldValue<VarT>{VariableIDMapT::GetValue(variableID), variableID}, constrainer);
         }
+        return true;
     }    
     
     void PopulateWorld(SolverState& state)