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edited Jul 8, 2019 at 21:27

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Mathematica, 2525 24 bytes

Tally@#~MatchQ~MatchQ[{{_,2}..}&]@*Tally

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The Tally function returns a list of the form {{elementelement, countcount}, ...}, which is then matched against a pattern that checks whether all countcount are 2.

Mathematica, 25 bytes

Tally@#~MatchQ~{{_,2}..}&

Try it online!

The Tally function returns a list of the form {{element, count}, ...}, which is then matched against a pattern that checks whether all count are 2.

Mathematica, 25 24 bytes

MatchQ[{{_,2}..}]@*Tally

Try it online!

The Tally function returns a list of the form {{element, count}, ...}, which is then matched against a pattern that checks whether all count are 2.

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created Jul 8, 2019 at 21:22

Doorknob

71.8k
20
143
385

Mathematica, 25 bytes

Tally@#~MatchQ~{{_,2}..}&

Try it online!

The Tally function returns a list of the form {{element, count}, ...}, which is then matched against a pattern that checks whether all count are 2.