Determine if a string has all unique characters: Difference between revisions
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This is a duplicate of the character at index 10.
[1] FALSE</pre>
=={{header|Racket}}==
<lang racket>#lang racket
(define (first-non-unique-element.index seq)
(let/ec ret
(for/fold ((es (hash))) ((e seq) (i (in-naturals)))
(if (hash-has-key? es e) (ret (list e (hash-ref es e) i)) (hash-set es e i)))
#f))
(define (report-if-a-string-has-all-unique-characters str)
(printf "~s (length ~a): ~a~%" str (string-length str)
(match (first-non-unique-element.index str)
[#f "contains all unique characters"]
[(list e i i′) (format "has character '~a' (0x~a) at index ~a (first seen at ~a)"
e (number->string (char->integer e) 16) i′ i)])))
(module+ main
(for-each report-if-a-string-has-all-unique-characters
(list "" "." "abcABC" "XYZ ZYX"
"1234567890ABCDEFGHIJKLMN0PQRSTUVWXYZ")))
</lang>
{{out}}
<pre>"" (length 0): contains all unique characters
"." (length 1): contains all unique characters
"abcABC" (length 6): contains all unique characters
"XYZ ZYX" (length 7): has character 'Z' (0x5a) at index 4 (first seen at 2)
"1234567890ABCDEFGHIJKLMN0PQRSTUVWXYZ" (length 36): has character '0' (0x30) at index 24 (first seen at 9)</pre>
=={{header|Raku}}==
(formerly Perl 6)
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