day 1

01/01.exs

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+list = File.read!("input.txt")
+|> String.split("\n")
+|> Enum.map(&String.to_integer/1)
+# pattern match binary tuple from list values
+[{a, b} | _] = for x <- list, y <- list, x + y == 2020, do: {x, y}
+IO.puts("Part 1: #{a * b}")
+# same thing but with 3-ary tuple
+[{a, b, c} | _] = for x <- list, y <- list, z <- list, x + y + z == 2020, do: {x, y, z}
+IO.puts("Part 2: #{a * b * c}")

01/01.py

@@ -0,0 +1,23 @@
+def part1():
+	with open('input.txt','r') as f:
+		expenses = [int(x) for x in f]
+		for a in expenses:
+			for b in expenses:
+				if a + b == 2020:
+					return a*b
+
+def part2():
+	with open('input.txt','r') as f:
+		expenses = [int(x) for x in f]
+		for a in expenses:
+			for b in expenses:
+				for c in expenses:
+					if a + b + c == 2020:
+						return a*b*c
+
+def main():
+	print(f'Part 1: {part1()}')
+	print(f'Part 2: {part2()}')
+
+if __name__ == "__main__":
+	main()

01/01.rb

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+def find_product_of(n)
+	puts File
+	.readlines("input.txt") # read input lines as array entries
+	.map(&:to_i) # convert each array entry to integer
+	.permutation(n) # create Enumerable with all permutations of n entries
+	.find { |array| array.sum == 2020} # find a permutation that sums to 2020
+	.inject(:*) # get the product of that array
+end
+
+puts "Part 1: "
+find_product_of(2)
+puts "Part 2: "
+find_product_of(3)

01/input.txt

@@ -0,0 +1,200 @@
+2004
+1823
+1628
+1867
+1073
+1951
+1909
+1761
+1093
+1992
+1986
+1106
+1537
+1905
+1233
+1961
+1760
+1562
+1781
+1329
+1272
+1660
+1367
+1248
+1697
+1515
+1470
+1980
+1884
+1784
+1966
+1778
+1426
+1255
+1089
+1748
+1253
+1870
+1651
+1131
+1623
+1595
+1128
+1014
+1863
+1855
+1203
+1395
+1521
+1365
+1202
+780
+1560
+1834
+1494
+1551
+1398
+1190
+1975
+1940
+1217
+1793
+1310
+1070
+1865
+1307
+1735
+1897
+1410
+1994
+1541
+1569
+1731
+1238
+1193
+1226
+1435
+1159
+1642
+1652
+1908
+1920
+1930
+1068
+1914
+1186
+1795
+1888
+1634
+1750
+1950
+1493
+1353
+1461
+1658
+1856
+1301
+1538
+1948
+1998
+1847
+1880
+1657
+1536
+1457
+1762
+1706
+1894
+542
+1991
+1108
+1072
+1064
+1511
+1496
+1480
+1955
+1604
+1766
+1983
+1713
+1234
+1503
+1583
+1729
+1140
+1006
+1600
+1699
+1280
+1891
+1996
+1375
+1167
+1625
+1129
+1770
+1497
+1620
+1267
+1421
+1399
+1563
+1636
+1293
+1506
+1613
+1958
+1967
+1182
+1050
+1947
+1787
+1774
+1928
+1896
+1303
+1826
+1132
+1254
+1752
+1510
+1705
+1229
+1558
+1989
+1567
+698
+1738
+1357
+1587
+1316
+1838
+1311
+1057
+1644
+1135
+1300
+1134
+1577
+1381
+1806
+1176
+1993
+1769
+1633
+1450
+1819
+1973
+1694
+969
+1987
+1095
+1717
+1933
+1593
+1045
+1355
+1459
+1619