36 lines
798 B
JavaScript
36 lines
798 B
JavaScript
(() => {
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'use strict';
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// isHappy :: Int -> Bool
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let isHappy = n => {
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let f = n => n.toString()
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.split('')
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.reduce((a, x) => a + Math.pow(parseInt(x, 10), 2), 0),
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p = (s, n) => n === 1 ? true : (
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s.has(n) ? false : p(s.add(n), f(n))
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);
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return p(new Set(), n);
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},
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// until :: (a -> Bool) -> (a -> a) -> a -> a
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until = (p, f, x) => {
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let v = x;
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while (!p(v)) v = f(v);
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return v;
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};
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return until(
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m => m.xs.length === 8,
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m => {
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let n = m.n;
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return {
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n: n + 1,
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xs: isHappy(n) ? m.xs.concat(n) : m.xs
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};
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}, {
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n: 1,
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xs: []
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}
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).xs;
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})();
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