2020 day1 - two/three sum

2020/day01/input.txt

@@ -0,0 +1,200 @@
+1593
+1575
+1583
+1609
+1835
+2008
+1638
+1396
+1833
+1524
+1778
+1574
+1653
+1962
+1831
+1557
+1847
+1587
+1876
+1914
+1565
+1585
+1713
+35
+1862
+1885
+1735
+1497
+1989
+1871
+1923
+1917
+1719
+1797
+1222
+1493
+1939
+1139
+1260
+1622
+1625
+1683
+1742
+1996
+1579
+1703
+1692
+1920
+1536
+1965
+1936
+1947
+1800
+1556
+1633
+1530
+1612
+1764
+1810
+1845
+1750
+1854
+1973
+1512
+1856
+1568
+1634
+1630
+1602
+1555
+1681
+1844
+1544
+1909
+1690
+1851
+1785
+863
+1866
+1988
+1715
+1881
+1570
+1380
+1956
+777
+1693
+1717
+1724
+1975
+790
+1484
+1822
+1922
+1963
+1741
+1809
+1896
+1837
+1980
+1244
+1832
+1834
+1643
+1775
+1818
+1503
+1802
+1957
+1174
+1826
+1649
+1941
+1571
+1930
+1629
+1502
+2002
+1700
+1880
+1723
+1803
+2007
+1543
+1872
+1993
+1740
+1919
+1688
+1067
+1680
+1580
+1558
+1772
+1694
+1480
+1257
+1796
+2001
+537
+1701
+1613
+1784
+1559
+1482
+1968
+1604
+983
+1842
+1817
+1850
+1788
+1982
+1535
+1615
+453
+1895
+1443
+1308
+1533
+1714
+1765
+1037
+1992
+1843
+1883
+1981
+1525
+1038
+1540
+1766
+1886
+1546
+1716
+810
+1899
+1708
+1508
+1870
+1051
+1867
+1840
+1617
+1726
+1566
+1616
+1948
+1771
+1627
+1994
+1486
+1913
+1600
+1983
+1501
+2003
+1667
+1620
+1943
+1674

2020/day01/main.go

@@ -3,6 +3,7 @@ package main
 import (
 	"flag"
 	"fmt"
+	"strings"
 
 	"github.com/alexchao26/advent-of-code-go/util"
 )
@@ -23,9 +24,44 @@ func main() {
 }
 
 func part1(input string) int {
-	return 0
+	parsed := parseInputs(input)
+
+	seen := map[int]bool{}
+
+	for _, n := range parsed {
+		if seen[n] {
+			return n * (2020 - n)
+		}
+		seen[2020-n] = true
+	}
+
+	return -1 // should not be hit
 }
 
 func part2(input string) int {
-	return 0
+	parsed := parseInputs(input)
+
+	// O(n^3) is fast enough
+	for i := 0; i < len(parsed); i++ {
+		for j := i + 1; j < len(parsed); j++ {
+			for k := j + 1; k < len(parsed); k++ {
+				if parsed[i]+parsed[j]+parsed[k] == 2020 {
+					return parsed[i] * parsed[j] * parsed[k]
+				}
+			}
+		}
+	}
+
+	return -1 // should not be hit
+}
+
+func parseInputs(input string) []int {
+	split := strings.Split(input, "\n")
+
+	nums := []int{}
+	for _, n := range split {
+		nums = append(nums, util.StrToInt(n))
+	}
+
+	return nums
 }

2020/day01/main_test.go

@@ -1,6 +1,10 @@
 package main
 
-import "testing"
+import (
+	"testing"
+
+	"github.com/alexchao26/advent-of-code-go/util"
+)
 
 var tests1 = []struct {
 	name  string
@@ -8,7 +12,13 @@ var tests1 = []struct {
 	input string
 	// add extra args if needed
 }{
-	// {"actual", ACTUAL_ANSWER, util.ReadFile("input.txt")},
+	{"example", 514579, `1721
+979
+366
+299
+675
+1456`},
+	{"actual", 1019371, util.ReadFile("input.txt")},
 }
 
 func TestPart1(t *testing.T) {
@@ -28,7 +38,13 @@ var tests2 = []struct {
 	input string
 	// add extra args if needed
 }{
-	// {"actual", ACTUAL_ANSWER, util.ReadFile("input.txt")},
+	{"example", 241861950, `1721
+979
+366
+299
+675
+1456`},
+	{"actual", 278064990, util.ReadFile("input.txt")},
 }
 
 func TestPart2(t *testing.T) {