58 lines
1.6 KiB
D
58 lines
1.6 KiB
D
import std.algorithm, std.range, std.traits, permutations2,
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permutations_by_swapping1;
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auto prod(Range)(/*in*/ Range r) /*pure nothrow*/ {
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return reduce!q{a * b}(cast(ForeachType!Range)1, r);
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}
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T permanent(T)(in T[][] a) /*pure nothrow*/
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in {
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foreach (const row; a)
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assert(row.length == a[0].length);
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} body {
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auto r = iota(cast()a.length);
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T tot = 0;
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foreach (sigma; permutations(r.array()))
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tot += r.map!(i => a[i][sigma[i]])().prod();
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return tot;
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}
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T determinant(T)(in T[][] a) /*pure nothrow*/
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in {
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foreach (const row; a)
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assert(row.length == a[0].length);
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} body {
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immutable n = a.length;
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auto r = iota(n);
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T tot = 0;
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//foreach (sigma, sign; spermutations(n)) {
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foreach (sigma_sign; spermutations(n)) {
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const sigma = sigma_sign[0];
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immutable sign = sigma_sign[1];
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tot += sign * r.map!(i => a[i][sigma[i]])().prod();
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}
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return tot;
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}
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void main() {
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import std.stdio;
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foreach (const a; [[[1, 2],
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[3, 4]],
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[[1, 2, 3, 4],
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[4, 5, 6, 7],
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[7, 8, 9, 10],
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[10, 11, 12, 13]],
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[[ 0, 1, 2, 3, 4],
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[ 5, 6, 7, 8, 9],
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[10, 11, 12, 13, 14],
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[15, 16, 17, 18, 19],
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[20, 21, 22, 23, 24]]]) {
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writefln("[%([%(%2s, %)],\n %)]]", a);
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writefln("Permanent: %s, determinant: %s\n",
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permanent(a), determinant(a));
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}
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}
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