Algorithm for finding circular references in a spreadsheet

Question

I have a spreadsheet application with formulas. I am looking for the best algorithm for detecting circular references among the formulas. The current approach I have is slow and

Answer 1

Perhaps you have motives for checking on your own, but Excel already checks for circular references automatically. You can use the Worksheets.CircularReference property in VBA to access this information.

Answer 2

Represent the dependencies between cells as a directed graph, and use Tarjan's strongly connected components algorithm (each strongly connected component of size 2 or larger contains cycles).

Answer 3

You need to do a topological sorting of the cells anyway in order to be able to rapidly calculate the values of cells when something is changed. The topological sorting procedure also detect cycles as a byproduct.

See http://en.wikipedia.org/wiki/Topological_sorting