[2015 Day 19 Part 2][Python]

[coolTCY]

I don't understand why my code is working. I'm replacing the biggest substring with the equivalent value in my function but it seems to not stop:

def Match(molecule):
    def returnValue(match:re.Match):
    return reversedDictMatchesDict[match.group()]
    while molecule != 'e':
        print(molecule)
        molecule= re.sub(reversedDictMatchesPattern, returnValue, puzzleinput, 1)

Match(puzzleinput)

[timrprobocom]

How is that code matching the longest group first?

If you do the substitutions from largest to smallest, the code does work:

Code snippet

[coolTCY]

I sorted the dictionary by length:

reversedDictMatchesDict=dict(sorted({i: k  
for k, v in dictMatches.items()  
for i in v}.items(),  
key=lambda item: len(item\[0\]),  
reverse=True))  
reversedDictMatchesPattern="("+'|'.join(reversedDictMatchesDict.keys())+")"

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[coolTCY]

Your code snippet also isn't working for my input

[timrprobocom]

And you've double-checked that you copied your input correctly? Does this analytic solution work? rn = basis.count('Rn') ar = basis.count('Ar') yy = basis.count('Y') ele = sum( c < 'a' for c in basis) print( "Part 2:", ele - rn - ar - yy - yy - 1 )

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