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How can we convert a list to an integer correctly?

{5, 22, 4, 5} -> 52245?

When I use the command FromDigits in Mathematica

FromDigits[{5, 22, 4, 5}]

The result is incorrect, namely 7245

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5 Answers 5

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Here are three ways to do it. The first is the best I think:

FromDigits@Flatten[IntegerDigits /@ {5, 22, 4, 5}]

ToExpression@StringJoin[ToString /@ {5, 22, 4, 5}]

ToExpression@StringJoin@StringCases[Characters@ToString@{5, 22, 4, 5}, DigitCharacter]
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0
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FromDigits @ ToString @ Row @ {5, 22, 4, 5}

Head[%]
52245

Integer
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5
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ToExpression@StringJoin@IntegerString[{5, 22, 4, 5}]

52245

ToExpression@StringJoin@IntegerString[{5, 22, 4, 5},#]&/@{2,10,16}

{10110110100101, 52245, 51645}

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{5, 22, 4, 5} ~ StringRiffle ~ "" // FromDigits
52245
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    $\begingroup$ Awesome. Never thought of StringRiffle $\endgroup$
    – user49048
    May 25, 2021 at 14:25
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list = {5, 22, 4, 5};
FromDigits[StringJoin[IntegerString[list]]]

which gives

52245
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