# UNDF: UNDF-2026-000000983
--- a/source/glest_game/world/unit_updater.h
+++ b/source/glest_game/world/unit_updater.h
@@ -1,6 +1,7 @@
 #ifndef _GLEST_GAME_UNITUPDATER_H_
 #define _GLEST_GAME_UNITUPDATER_H_

+#include <unordered_set>
 #include <vector>

 ...
@@ -127,7 +128,7 @@
     vector<Unit *> findUnitsInRange(const Unit *unit, int radius);

 private:
-    void findUnitsForCell(Cell *cell, vector<Unit *> &units);
+    void findUnitsForCell(Cell *cell, vector<Unit *> &units, std::unordered_set<int> &seenIds);

--- a/source/glest_game/world/unit_updater.cpp
+++ b/source/glest_game/world/unit_updater.cpp
@@ -3461,13 +3461,10 @@
-void UnitUpdater::findUnitsForCell(Cell *cell, vector<Unit *> &units) {
+void UnitUpdater::findUnitsForCell(Cell *cell, vector<Unit *> &units, std::unordered_set<int> &seenIds) {
     // all fields
     if (cell != NULL) {
         for (int k = 0; k < fieldCount; k++) {
             Field f = static_cast<Field>(k);

             // check field
             Unit *cellUnit = cell->getUnit(f);

             if (cellUnit != NULL && cellUnit->isAlive()) {
-                // check if unit already is in list
-                bool found = false;
-                for (unsigned int i = 0; i < units.size(); ++i) {
-                    Unit *unitInList = units[i];
-                    if (unitInList->getId() == cellUnit->getId()) {
-                        found = true;
-                        break;
-                    }
-                }
-                if (found == false) {
+                // O(1) dedup via hash set instead of O(U) linear scan
+                if (seenIds.insert(cellUnit->getId()).second) {
                     units.push_back(cellUnit);
                 }
             }
@@ -3492,6 +3489,8 @@
 vector<Unit *> UnitUpdater::findUnitsInRange(const Unit *unit, int radius) {
     int range = radius;
     vector<Unit *> units;
+    std::unordered_set<int> seenIds;

     // aux vars
     int size = unit->getType()->getSize();
@@ -3507,7 +3506,7 @@
 #endif
                 Cell *cell = map->getCell(i, j);
-                findUnitsForCell(cell, units);
+                findUnitsForCell(cell, units, seenIds);
             }
         }
     }