/usr/include/geos/algorithm/ is in libgeos-dev 3.2.2-3ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/geos/algorithm/Angle.h
/usr/include/geos/algorithm/BoundaryNodeRule.h
/usr/include/geos/algorithm/CGAlgorithms.h
/usr/include/geos/algorithm/CentralEndpointIntersector.h
/usr/include/geos/algorithm/CentroidArea.h
/usr/include/geos/algorithm/CentroidLine.h
/usr/include/geos/algorithm/CentroidPoint.h
/usr/include/geos/algorithm/ConvexHull.h
/usr/include/geos/algorithm/ConvexHull.inl
/usr/include/geos/algorithm/ExtractLineByLocation.h
/usr/include/geos/algorithm/HCoordinate.h
/usr/include/geos/algorithm/InteriorPointArea.h
/usr/include/geos/algorithm/InteriorPointLine.h
/usr/include/geos/algorithm/InteriorPointPoint.h
/usr/include/geos/algorithm/LengthIndexOfPoint.h
/usr/include/geos/algorithm/LengthIndexedLine.h
/usr/include/geos/algorithm/LengthLocationMap.h
/usr/include/geos/algorithm/LineIntersector.h
/usr/include/geos/algorithm/LinearGeometryBuilder.h
/usr/include/geos/algorithm/LinearIterator.h
/usr/include/geos/algorithm/LinearLocation.h
/usr/include/geos/algorithm/LocationIndexOfLine.h
/usr/include/geos/algorithm/LocationIndexOfPoint.h
/usr/include/geos/algorithm/MCPointInRing.h
/usr/include/geos/algorithm/MinimumDiameter.h
/usr/include/geos/algorithm/NotRepresentableException.h
/usr/include/geos/algorithm/PointInRing.h
/usr/include/geos/algorithm/PointLocator.h
/usr/include/geos/algorithm/RayCrossingCounter.h
/usr/include/geos/algorithm/RobustDeterminant.h
/usr/include/geos/algorithm/SIRtreePointInRing.h
/usr/include/geos/algorithm/SimplePointInRing.h
/usr/include/geos/algorithm/distance/
/usr/include/geos/algorithm/distance/DiscreteHausdorffDistance.h
/usr/include/geos/algorithm/distance/DistanceToPoint.h
/usr/include/geos/algorithm/distance/PointPairDistance.h
/usr/include/geos/algorithm/locate/
/usr/include/geos/algorithm/locate/IndexedPointInAreaLocator.h
/usr/include/geos/algorithm/locate/PointOnGeometryLocator.h
/usr/include/geos/algorithm/locate/SimplePointInAreaLocator.h