A Graph-Theoretic Model for a Generic Three-Jug Puzzle
Suresh Manjanath Hegde, Shashanka Kulamarva
TL;DR
This work addresses the generic three-jug puzzle by introducing a graph-theoretic framework that abstracts state transitions into a directed graph $G_Q$ built from an ordered quadruple $Q=(a,b,c,d)$ with $a>b>c$, $d=2k$, and $b\ge k$. A central result proves that an edge in $G_P$ corresponds exactly to a single measurable pour between distributions, and that a directed path from $s=(\tilde b,\tilde c)$ to $t=(\frac{d}{2},0)$ in $G_P$ is equivalent to the existence of a solution to the puzzle $\mathbb{P}^{\tilde a,\tilde b,\tilde c}_{a,b,c}$; this provides a concrete solvability criterion. The paper then sketches an algorithm: form $Q$, build $G_Q$, check for an $st$-path, and, if present, follow a shortest path to obtain a minimal-pours solution; otherwise, conclude unsolvability. The approach yields a puzzle-independent method with potential for efficient computation and extension to related liquid-transfer problems, offering a formal, graph-based lens on state-space exploration and optimal strategies.
Abstract
A classic three-jug puzzle asks, given three jugs $A$, $B$, and $C$ with fixed maximum capacities, with jug $A$ filled with wine to its maximum capacity, whether is it possible to divide the wine into two halves by pouring it from one jug to another without using any other measuring devices. However, we consider a generic version of the three-jug puzzle and present an independent graph-theoretic model to determine whether the puzzle has a solution at all. If it has a solution, then the same can be determined using this model. We also present the sketch of an algorithm to determine the solution of the puzzle.
