Determine if a string has all unique characters: Difference between revisions

Content added Content deleted
(→‎{{header|JavaScript}}: Updated alternative to grouping and sorting)
m (→‎{{header|JavaScript}}: Updated output of group and sort example, used sortOn in lieu of sortBy)
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duplicates = filter(g => 1 < g.length)(
duplicates = filter(g => 1 < g.length)(
groupBy(on(eq)(snd))(
groupBy(on(eq)(snd))(
sortBy(comparing(snd))(
sortOn(snd)(
zip(enumFrom(0))(chars(s))
zip(enumFrom(0))(chars(s))
)
)
Line 576: Line 576:
return 0 < duplicates.length ? Just(
return 0 < duplicates.length ? Just(
fanArrow(compose(snd, fst))(map(fst))(
fanArrow(compose(snd, fst))(map(fst))(
sortBy(comparing(compose(fst, fst)))(
sortOn(compose(fst, fst))(
duplicates
duplicates
)[0]
)[0]
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console.log(
console.log(
fTable('First duplicated character, if any:')(
fTable('First duplicated character, if any:')(
s => `'${s}'`
s => `'${s}' (${s.length})`
)(maybe('None')(tpl => {
)(maybe('None')(tpl => {
const [c, ixs] = Array.from(tpl);
const [c, ixs] = Array.from(tpl);
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// chars :: String -> [Char]
// chars :: String -> [Char]
const chars = s => s.split('');
const chars = s => s.split('');

// comparing :: (a -> b) -> (a -> a -> Ordering)
const comparing = f =>
⚫
x => y => {
⚫
const
⚫
a = f(x),
⚫
b = f(y);
⚫
return a < b ? -1 : (a > b ? 1 : 0);
};


// compose (<<<) :: (b -> c) -> (a -> b) -> a -> c
// compose (<<<) :: (b -> c) -> (a -> b) -> a -> c
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const snd = tpl => tpl[1];
const snd = tpl => tpl[1];


// sortBy :: (a -> a -> Ordering) -> [a] -> [a]
// sortOn :: Ord b => (a -> b) -> [a] -> [a]
const sortBy = f => xs =>
const sortOn = f =>
// Equivalent to sortBy(comparing(f)), but with f(x)
xs.slice()
// evaluated only once for each x in xs.
.sort(uncurry(f));
// ('Schwartzian' decorate-sort-undecorate).
⚫
xs => xs.map(
⚫
x => [f(x), x]
⚫
).sort(
⚫
(a, b) => a[0] < b[0] ? -1 : (a[0] > b[0] ? 1 : 0)
⚫
).map(x => x[1]);


// take :: Int -> [a] -> [a]
// take :: Int -> [a] -> [a]
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{{Out}}
{{Out}}
<pre>First duplicated character, if any:
<pre>First duplicated character, if any:
'' -> None
'' (0) -> None
'.' -> None
'.' (1) -> None
'abcABC' -> None
'abcABC' (6) -> None
'XYZ ZYX' -> 'X' (0x58) at 0, 6
'XYZ ZYX' (7) -> 'X' (0x58) at 0, 6
'1234567890ABCDEFGHIJKLMN0PQRSTUVWXYZ' -> '0' (0x30) at 9, 24</pre>
'1234567890ABCDEFGHIJKLMN0PQRSTUVWXYZ' (36) -> '0' (0x30) at 9, 24</pre>




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