103 lines
3.0 KiB
JavaScript
103 lines
3.0 KiB
JavaScript
(function (n) {
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'use strict';
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// PASCAL TRIANGLE --------------------------------------------------------
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// pascal :: Int -> [[Int]]
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function pascal(n) {
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return foldl(function (a) {
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var xs = a.slice(-1)[0]; // Previous row
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return append(a, [zipWith(
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function (a, b) {
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return a + b;
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},
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append([0], xs),
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append(xs, [0])
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)]);
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}, [
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[1] // Initial seed row
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], enumFromTo(1, n - 1));
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};
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// GENERIC FUNCTIONS ------------------------------------------------------
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// (++) :: [a] -> [a] -> [a]
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function append(xs, ys) {
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return xs.concat(ys);
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};
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// enumFromTo :: Int -> Int -> [Int]
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function enumFromTo(m, n) {
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return Array.from({
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length: Math.floor(n - m) + 1
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}, function (_, i) {
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return m + i;
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});
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};
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// foldl :: (b -> a -> b) -> b -> [a] -> b
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function foldl(f, a, xs) {
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return xs.reduce(f, a);
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};
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// foldr (a -> b -> b) -> b -> [a] -> b
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function foldr(f, a, xs) {
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return xs.reduceRight(f, a);
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};
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// map :: (a -> b) -> [a] -> [b]
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function map(f, xs) {
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return xs.map(f);
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};
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// min :: Ord a => a -> a -> a
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function min(a, b) {
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return b < a ? b : a;
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};
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// zipWith :: (a -> b -> c) -> [a] -> [b] -> [c]
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function zipWith(f, xs, ys) {
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return Array.from({
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length: min(xs.length, ys.length)
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}, function (_, i) {
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return f(xs[i], ys[i]);
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});
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};
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// TEST and FORMAT --------------------------------------------------------
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var lstTriangle = pascal(n);
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// [[a]] -> bool -> s -> s
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function wikiTable(lstRows, blnHeaderRow, strStyle) {
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return '{| class="wikitable" ' + (strStyle ? 'style="' + strStyle +
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'"' : '') + lstRows.map(function (lstRow, iRow) {
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var strDelim = blnHeaderRow && !iRow ? '!' : '|';
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return '\n|-\n' + strDelim + ' ' + lstRow.map(function (v) {
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return typeof v === 'undefined' ? ' ' : v;
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})
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.join(' ' + strDelim + strDelim + ' ');
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})
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.join('') + '\n|}';
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}
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var lstLastLine = lstTriangle.slice(-1)[0],
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lngBase = lstLastLine.length * 2 - 1,
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nWidth = lstLastLine.reduce(function (a, x) {
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var d = x.toString()
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.length;
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return d > a ? d : a;
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}, 1) * lngBase;
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return [wikiTable(lstTriangle.map(function (lst) {
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return lst.join(';;')
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.split(';');
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})
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.map(function (line, i) {
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var lstPad = Array((lngBase - line.length) / 2);
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return lstPad.concat(line)
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.concat(lstPad);
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}), false, 'text-align:center;width:' + nWidth + 'em;height:' + nWidth +
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'em;table-layout:fixed;'), JSON.stringify(lstTriangle)].join('\n\n');
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})(7);
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