Advent of Code Solutions
advent-of-code
aoc
2015: Day 4
+45
+1
2015/04/part1-tests/input1
+1
2015/04/part1-tests/input1
···
1
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abcdef
+1
2015/04/part1-tests/input2
+1
2015/04/part1-tests/input2
···
1
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pqrstuv
+41
2015/04/solution.erl
+41
2015/04/solution.erl
···
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#!/usr/bin/env escript
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% --- Part 1 Code
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part1(Input) ->
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io:format("Part 1: ~b~n", [find_hash_with_prefix("00000", Input)]).
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find_hash_with_prefix(PrefixMatch, Input) ->
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find_hash_with_prefix(PrefixMatch, Input, 0).
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find_hash_with_prefix(PrefixMatch, Input, CurrentNumber) ->
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Hash = binary:encode_hex(crypto:hash(md5, [Input, integer_to_list(CurrentNumber)])),
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Prefix = string:slice(binary_to_list(Hash), 0, length(PrefixMatch)),
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if
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Prefix == PrefixMatch -> CurrentNumber;
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true -> find_hash_with_prefix(PrefixMatch, Input, CurrentNumber + 1)
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end.
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% --- Part 2 Code
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part2(Input) ->
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io:format("Part 2: ~b~n", [find_hash_with_prefix("000000", Input)]).
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% --- Generic Helper Functions
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read_input() -> read_input("").
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read_input(PrevLine) ->
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case io:fread("", "~s") of
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eof -> PrevLine;
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{error, _} -> halt(1);
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{ok, Terms} -> read_input(PrevLine ++ Terms)
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end.
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main(Args) ->
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Input = read_input(),
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case Args of
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["1"] ->
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part1(Input);
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["2"] ->
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part2(Input);
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_ ->
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part1(Input),
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part2(Input)
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end.