29 lines
1.3 KiB
Plaintext
29 lines
1.3 KiB
Plaintext
There are several so-called "self-describing" or "[[wp:Self-descriptive number|self-descriptive]]" integers.
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An integer is said to be "self-describing" if it has the property that, when digit positions are labeled 0 to N-1, the digit in each position is equal to the number of times that that digit appears in the number.
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For example, '''2020''' is a four-digit self describing number:
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* position 0 has value 2 and there are two 0s in the number;
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* position 1 has value 0 and there are no 1s in the number;
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* position 2 has value 2 and there are two 2s;
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* position 3 has value 0 and there are zero 3s.
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<br>
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Self-describing numbers < 100.000.000 are: 1210, 2020, 21200, 3211000, 42101000.
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;Task Description
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# Write a function/routine/method/... that will check whether a given positive integer is self-describing.
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# As an optional stretch goal - generate and display the set of self-describing numbers.
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;Related tasks:
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* [[Fours is the number of letters in the ...]]
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* [[Look-and-say sequence]]
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* [[Number names]]
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* [[Self-referential sequence]]
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* [[Spelling of ordinal numbers]]
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<br><br>
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