29 lines
676 B
D
Executable file
29 lines
676 B
D
Executable file
#!/usr/bin/env dub
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/+ dub.sdl:
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name "main"
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dependency "mir-algorithm" version="~>3.10.12"
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+/
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import std;
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import mir.combinatorics;
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void main()
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{
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File("input", "r").byLine.map!(to!int).array.multiplyNEntriesThatSumTo(3, 2020).writeln;
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}
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alias product = partial!(reverseArgs!(fold!((a, b) => a * b)), 1);
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int multiplyNEntriesThatSumTo(int[] input, int n, int requiredSum)
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{
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return input.combinations(n).filter!(combination => combination.sum == requiredSum)
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.map!(combination => combination.product)
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.front;
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}
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unittest
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{
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auto input = [1721, 979, 366, 299, 675, 1456];
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assert(input.multiplyNEntriesThatSumTo(3, 2020) == 241_861_950);
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}
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