## Problem You are given a list of chemical reaction rules: `A + B -> C` means combining elements A and B produces C. Given an initial set of elements, simulate the reactions until no more reactions are possible, then return the final stable set. Reactions trigger in any order when the required elements are both present. An element is consumed when it participates in a reaction. ```python def simulate_reactions( initial: list[str], rules: list[tuple[str, str, str]] # (reactant1, reactant2, product) ) -> list[str]: ... ``` ``` rules: [("H","O","W"), ("W","C","X"), ("H","N","Y")] initial: ["H", "H", "O", "C", "N"] Step 1: H+O -> W remaining: [H, C, N, W] Step 2: W+C -> X remaining: [H, N, X] Step 3: H+N -> Y remaining: [X, Y] No more rules apply. Output: ["X", "Y"] ``` ## Follow-ups 1. The order of reactions can affect the final state (some reactions compete for the same element). How would you detect and report all possible stable end states? 2. What data structure lets you efficiently find which rules are currently triggered given the current element multiset? 3. How do you detect infinite loops (A+B->A+B is a degenerate rule)? 4. Extend to support catalytic reactions where element C is consumed then reproduced (e.g. C remains after A+B+C->D+C).

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Chemical Reaction Simulation: Model Chain Reactions and Find Stable End States

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Problem You are given a list of chemical reaction rules: A + B -> C means combining elements A and B produces C. Given an initial set of elements, simulate the reactions until no more reactions are possible, then return the final stable set. Reactions trigger in any order when the required elements are both present. An element is consumed when it participates in a reaction. Follow-ups The order of reactions can affect the final state (some reactions compete for the same element). How would you d…

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This is a reported interview question from a hudson river trading interview during the oa round.

It covers the following topics: Coding, Oa .

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Chemical Reaction Simulation: Model Chain Reactions and Find Stable End States

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