HHammond / DailyProgrammer-236-Balancing-Chemical-Equations

A solution to Reddit's daily programmer hard difficulty challenge 236

[2015-10-16] Challenge 236 [Hard] Balancing chemical equations

https://www.reddit.com/r/dailyprogrammer/comments/3oz82g/20151016_challenge_236_hard_balancing_chemical/

The program takes as input from STDIN a list of strings representing chemical equations in standard form and returns strings of the balanced equations or explaining that the equation couldn't be solved by this program.

The solution is computed by converting the chemical equation into a homogeneous linear system and computing an integer solution which belongs to the nullspace of the system.

Usage:

julia chem.jl < equations.txt

Issues:

• There are valid equations which this program fails to balance (e.g. (CuOH)2CO3 -> CuO + CO2 + H2O).
• Sometimes it computes negative values (e.g. U3O8 + HNO3 -> UO2(NO3)2 + NO2 + H2O maps to U3O8 + -4HNO3 -> 3UO2(NO3)2 + -10NO2 + -2H2O)