| 1 | 'use strict';
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| 2 | function concat$(x, ...ys) {
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| 3 | for (var y of ys)
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| 4 | x.push(...y);
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| 5 | return x;
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| 6 | }
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| 7 | function splice(x, i, n = x.length - i, ...vs) {
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| 8 | return concat$(x.slice(0, i), vs, x.slice(i + n));
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| 9 | }
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| 10 | function* permutationsOf(x, n) {
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| 11 | var X = x.length;
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| 12 | if (X === 0 || n === 0) {
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| 13 | yield [];
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| 14 | return;
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| 15 | }
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| 16 | for (var i = 0; i < X; i++) {
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| 17 | var y = splice(x, i, 1);
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| 18 | for (var p of permutationsOf(y, n - 1))
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| 19 | yield [x[i], ...p];
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| 20 | }
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| 21 | }
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| 22 | function* permutations(x, n = -1) {
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| 23 | var X = x.length;
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| 24 | if (n > X)
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| 25 | return;
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| 26 | for (var i = n < 0 ? 0 : n, I = n < 0 ? X : n; i <= I; i++)
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| 27 | yield* permutationsOf(x, i);
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| 28 | }
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| 29 | module.exports = permutations;
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