24 Solver

A web app that finds all arithmetic expressions using 4 integers that equal 24.

Live: https://srihari-ganesh.github.io/24solver

How it works

Given 4 integers, the solver enumerates every valid Reverse Polish Notation expression using those numbers and the operators +, -, *, /. Arithmetic is done with exact rational fractions to avoid floating-point errors (e.g. 8 / (3 - 8/3) = 24 resolves correctly).

Algorithm:

1. Generate all combinations of 3 operators from {+, -, *, /} (4³ = 64 combos)
2. For each combo, form a 7-token sequence (4 numbers + 3 operators)
3. Enumerate all permutations of those 7 tokens (up to 5040)
4. Filter to valid RPN sequences, evaluate with rational arithmetic
5. Collect infix representations in a Set for deduplication

Total work per query: ≤ 64 × 5040 = 322,560 evaluations — runs instantly in the browser.

Classic test cases

Input	Result
3 3 8 8	(8 / (3 - (8 / 3))) (and others)
1 1 1 1	No solution
4 4 4 4	(4 - 4 + 4) * 4 (and others)
1 1 11 11	Addition-only solutions

Deployment

Pure static HTML/CSS/JS — no build step needed.

1. Create a repo named 24solver on GitHub under your account
2. Push index.html (and this README)
3. In repo Settings → Pages, set source to the main branch root
4. Site goes live at https://<username>.github.io/24solver