From c0830f24df390eb45a7395b92fa2d031f3f16877 Mon Sep 17 00:00:00 2001 From: Shadowfacts Date: Tue, 1 Dec 2020 00:14:57 -0500 Subject: [PATCH] Day 1 --- lib/day1/day1.ex | 73 +++++++++++++++++ lib/day1/input.txt | 200 +++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 273 insertions(+) create mode 100644 lib/day1/day1.ex create mode 100644 lib/day1/input.txt diff --git a/lib/day1/day1.ex b/lib/day1/day1.ex new file mode 100644 index 0000000..3e21e74 --- /dev/null +++ b/lib/day1/day1.ex @@ -0,0 +1,73 @@ +defmodule Day1 do + @example_1 """ + 1721 + 979 + 366 + 299 + 675 + 1456 + """ + + def part1(example \\ false) do + if(example, do: @example_1, else: File.read!("lib/day1/input.txt")) + |> String.trim() + |> String.split("\n") + |> Enum.map(&String.to_integer/1) + |> all_pairs() + |> find_sum_to_2020() + end + + def part2(example \\ false) do + if(example, do: @example_1, else: File.read!("lib/day1/input.txt")) + |> String.trim() + |> String.split("\n") + |> Enum.map(&String.to_integer/1) + |> all_triples() + |> find_sum_to_2020() + end + + def all_pairs(items) do + items + |> Enum.drop(-1) + |> Enum.with_index() + |> Enum.flat_map(fn {a, a_index} -> + {_, rest} = Enum.split(items, a_index + 1) + + Enum.map(rest, fn b -> + {a, b} + end) + end) + end + + def all_triples(items) do + items + |> Enum.drop(-1) + |> Enum.with_index() + |> Enum.flat_map(fn {a, a_index} -> + {_, rest} = Enum.split(items, a_index + 1) + + rest + |> Enum.drop(-1) + |> Enum.with_index() + |> Enum.flat_map(fn {b, b_index} -> + {_, rest_rest} = Enum.split(rest, b_index + 1) + + Enum.map(rest_rest, fn c -> + {a, b, c} + end) + end) + end) + end + + def find_sum_to_2020(groups) do + Enum.find_value(groups, fn items -> + list = Tuple.to_list(items) + + if Enum.reduce(list, 0, &(&1 + &2)) == 2020 do + Enum.reduce(list, 1, &(&1 * &2)) + else + nil + end + end) + end +end diff --git a/lib/day1/input.txt b/lib/day1/input.txt new file mode 100644 index 0000000..208b522 --- /dev/null +++ b/lib/day1/input.txt @@ -0,0 +1,200 @@ +1695 +1157 +1484 +1717 +622 +1513 +1924 +63 +1461 +1971 +1382 +1587 +1913 +1665 +1464 +1914 +1637 +1527 +1424 +1361 +1187 +272 +1909 +1448 +1623 +1164 +1931 +1646 +1096 +1655 +1962 +1961 +1694 +1792 +1989 +1616 +138 +1887 +1357 +1965 +1085 +308 +2007 +1254 +1179 +1124 +1719 +1467 +1928 +1630 +1676 +1359 +1241 +1511 +1413 +1656 +1818 +1919 +1422 +1745 +1208 +1609 +1544 +1775 +1154 +1057 +1440 +1242 +1202 +1266 +1305 +1836 +1760 +1730 +1396 +1315 +1496 +1964 +1300 +1195 +1583 +1607 +1743 +1682 +1453 +1848 +1320 +1601 +954 +1473 +1847 +1486 +1853 +1668 +1342 +1087 +1139 +1349 +1568 +1728 +1420 +1233 +1073 +1376 +1658 +1477 +1871 +1958 +1950 +1503 +1758 +1474 +1203 +1336 +1981 +1309 +1618 +1846 +1974 +1940 +1333 +1119 +1756 +1918 +961 +1307 +1375 +1346 +1611 +1284 +84 +1754 +1608 +2010 +1341 +1136 +1218 +1882 +1911 +1288 +1930 +1749 +1952 +1556 +1757 +1761 +1112 +1963 +1186 +1373 +1622 +1973 +1330 +1508 +1222 +1226 +1389 +1679 +1584 +1237 +1563 +1763 +1998 +1293 +1642 +95 +1661 +1674 +1100 +1262 +1895 +1548 +1400 +1205 +1435 +1156 +1034 +1577 +1701 +1198 +1173 +1500 +1858 +1809 +1780 +1412 +1982 +1070 +1523 +1776 +1598 +1113 +1144 +1777 +1313 +1102 +1999 +1405 +1784 +1196