senipah/subset-sum-reconciler

This is a subset sum problem solver written in Excel VBA

Subset Sum Reconciler

Introduction

This is a subset sum problem solver written in Excel VBA.

A common question in Excel is "I have a list of numbers and I want to see which of them add up to a specific total".

This is something most people think should be fairly trivial to achieve in Excel. In reality, however, it ain't all that easy. The question is a variation on a well known problem in computer science called the Subset sum problem.

It can be done with Solver, but there is a variable limit and Solver will only return one possible solution.

As it is something that crops up so often I thought I'd share a workbook I have that can calculate this. Click here to download it (xlsm file). This file uses VBA to do the calculation. It uses dynamic programming to offset time complexity with space complexity but given a big list of numbers it still may take too long to be feasible.

Dependencies

This file depends on (and includes) a copy of my VBA-Better-Array library. If you don't want to use this it is possible to alter the code to use VBA's built in Collection or Array types without too much effort.