Sort SOP
https://gyazo.com/a345d768e57949f70a6115c1a666594f
In Houdini, points and primitives have an inherent order, and each point/primitive knows its own “point number” or “primitive number” (its index within the list of points/primitives). This node lets you change the order of points/primitives based on certain criteria.
To change the order of vertices within a primitive, use the Reverse SOP.iconReverse SOP instead.