100 lines
2.7 KiB
JavaScript
100 lines
2.7 KiB
JavaScript
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(() => {
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// TRAVERSALS -------------------------------------------------------------
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// preorder Tree a -> [a]
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const preorder = a => [a[v]]
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.concat(a[l] ? preorder(a[l]) : [])
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.concat(a[r] ? preorder(a[r]) : []);
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// inorder Tree a -> [a]
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const inorder = a =>
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(a[l] ? inorder(a[l]) : [])
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.concat(a[v])
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.concat(a[r] ? inorder(a[r]) : []);
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// postorder Tree a -> [a]
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const postorder = a =>
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(a[l] ? postorder(a[l]) : [])
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.concat(a[r] ? postorder(a[r]) : [])
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.concat(a[v]);
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// levelorder Tree a -> [a]
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const levelorder = a => (function go(x) {
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return x.length ? (
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x[0] ? (
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[x[0][v]].concat(
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go(x.slice(1)
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.concat([x[0][l], x[0][r]])
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)
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)
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) : go(x.slice(1))
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) : [];
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})([a]);
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// GENERIC FUNCTIONS -----------------------------------------------------
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// A list of functions applied to a list of arguments
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// <*> :: [(a -> b)] -> [a] -> [b]
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const ap = (fs, xs) => //
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[].concat.apply([], fs.map(f => //
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[].concat.apply([], xs.map(x => [f(x)]))));
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// intercalate :: String -> [a] -> String
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const intercalate = (s, xs) => xs.join(s);
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// justifyLeft :: Int -> Char -> Text -> Text
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const justifyLeft = (n, cFiller, strText) =>
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n > strText.length ? (
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(strText + cFiller.repeat(n))
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.substr(0, n)
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) : strText;
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// unlines :: [String] -> String
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const unlines = xs => xs.join('\n');
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// unwords :: [String] -> String
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const unwords = xs => xs.join(' ');
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// zipWith :: (a -> b -> c) -> [a] -> [b] -> [c]
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const zipWith = (f, xs, ys) =>
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Array.from({
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length: Math.min(xs.length, ys.length)
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}, (_, i) => f(xs[i], ys[i]));
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// TEST -------------------------------------------------------------------
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// asciiTree :: String
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const asciiTree = unlines([
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' 1',
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' / \\',
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' / \\',
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' / \\',
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' 2 3',
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' / \\ /',
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' 4 5 6',
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' / / \\',
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' 7 8 9'
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]);
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const [v, l, r] = [0, 1, 2],
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tree = [1, [2, [4, [7]],
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[5]
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],
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[3, [6, [8],
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[9]
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]]
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],
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// fs :: [(Tree a -> [a])]
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fs = [preorder, inorder, postorder, levelorder];
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return asciiTree + '\n\n' +
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intercalate('\n',
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zipWith(
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(f, xs) => justifyLeft(12, ' ', f.name + ':') + unwords(xs),
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fs,
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ap(fs, [tree])
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)
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);
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})();
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