Advent of Code Solutions
advent-of-code
aoc
2015: Day 3
+84
+1
2015/03/part1-tests/input1
+1
2015/03/part1-tests/input1
···
1
+
>
+1
2015/03/part1-tests/input2
+1
2015/03/part1-tests/input2
···
1
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^>v<
+1
2015/03/part1-tests/input3
+1
2015/03/part1-tests/input3
···
1
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^v^v^v^v^v
+1
2015/03/part2-tests/input1
+1
2015/03/part2-tests/input1
···
1
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^v
+1
2015/03/part2-tests/input2
+1
2015/03/part2-tests/input2
···
1
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^>v<
+1
2015/03/part2-tests/input3
+1
2015/03/part2-tests/input3
···
1
+
^v^v^v^v^v
+72
2015/03/solution.erl
+72
2015/03/solution.erl
···
1
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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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InitialPosition = {0, 0},
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InitialMap = #{InitialPosition => 1},
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io:format("Part 1: ~b~n", [length(maps:keys(process_instructions(InitialMap, InitialPosition, Input)))]).
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visit_house(HouseMap, Position) ->
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CurrentValue = maps:get(Position, HouseMap, 0),
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maps:put(Position, CurrentValue + 1, HouseMap).
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process_instructions(HouseMap, _, "\n") ->
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HouseMap;
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process_instructions(HouseMap, Position, Input) ->
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{CurrentX, CurrentY} = Position,
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NewPos = case {_, Rest} = next_char(Input) of
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{"^", _} -> {CurrentX, CurrentY + 1};
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{"<", _} -> {CurrentX - 1, CurrentY};
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{"v", _} -> {CurrentX, CurrentY - 1};
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{">", _} -> {CurrentX + 1, CurrentY}
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end,
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process_instructions(visit_house(HouseMap, NewPos), NewPos, Rest).
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% --- Part 2 Code
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part2(Input) ->
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InitialPositionMap = #{santa => {0, 0}, robo_santa => {0, 0}},
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InitialMap = #{{0, 0} => 2},
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Mover = santa,
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io:format("Part 2: ~b~n", [length(maps:keys(process_instructions(InitialMap, InitialPositionMap, Mover, Input)))]).
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update_position(PositionMap, Mover, Movement) ->
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{CurrentX, CurrentY} = maps:get(Mover, PositionMap),
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case Movement of
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up -> maps:put(Mover, {CurrentX, CurrentY + 1}, PositionMap);
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left -> maps:put(Mover, {CurrentX - 1, CurrentY}, PositionMap);
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down -> maps:put(Mover, {CurrentX, CurrentY - 1}, PositionMap);
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right -> maps:put(Mover, {CurrentX + 1, CurrentY}, PositionMap)
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end.
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process_instructions(HouseMap, _, _, "\n") ->
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HouseMap;
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process_instructions(HouseMap, PositionMap, Mover, Input) ->
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NextMover = case Mover of santa -> robo_santa; robo_santa-> santa end,
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NewPosMap = case {_, Rest} = next_char(Input) of
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{"^", _} -> update_position(PositionMap, Mover, up);
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{"<", _} -> update_position(PositionMap, Mover, left);
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{"v", _} -> update_position(PositionMap, Mover, down);
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{">", _} -> update_position(PositionMap, Mover, right)
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end,
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process_instructions(visit_house(HouseMap, maps:get(Mover, NewPosMap)), NewPosMap, NextMover, Rest).
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% --- Generic Helper Functions
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next_char([Char | String]) -> {[Char], String}.
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read_input() -> read_input("").
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read_input(PrevLine) ->
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case io:get_chars("", 8192) of
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eof -> PrevLine;
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Data -> read_input(PrevLine ++ Data)
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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.