day 1

01/input

@@ -0,0 +1,200 @@
+1711
+1924
+1384
+1590
+1876
+1918
+2003
+1514
+1608
+1984
+1706
+1375
+1476
+1909
+1615
+1879
+1940
+1945
+1899
+1510
+1657
+1685
+1588
+1884
+1864
+1995
+1648
+1713
+1532
+1556
+1572
+1667
+1861
+1773
+1501
+1564
+1756
+395
+1585
+1717
+1553
+1487
+1617
+1808
+1780
+1570
+1881
+1992
+1894
+1772
+1837
+2002
+1659
+1731
+1873
+1760
+552
+1575
+1597
+1986
+1416
+1398
+1737
+1027
+1457
+198
+1904
+1753
+1727
+633
+1577
+1944
+1369
+1400
+1843
+1966
+1008
+1681
+1890
+1939
+1605
+1548
+1953
+1839
+1409
+1592
+1744
+1761
+1613
+1412
+1759
+703
+1498
+1941
+1425
+1528
+1469
+1728
+1447
+1406
+1797
+1543
+1682
+1722
+1723
+1893
+1644
+796
+1505
+1715
+1729
+1943
+1626
+1602
+1964
+1509
+1816
+1660
+1399
+1996
+1750
+1701
+1963
+1979
+1558
+1506
+1465
+2001
+1935
+1616
+1990
+1946
+1818
+1892
+1431
+1832
+1688
+2004
+1424
+1716
+1897
+1931
+1557
+1389
+1872
+1640
+1670
+1911
+1427
+1730
+211
+1420
+1488
+1689
+1383
+1967
+1594
+642
+1622
+1627
+1607
+1372
+1596
+1451
+1693
+1380
+1745
+1908
+1785
+1646
+1824
+1418
+1258
+1664
+1631
+1459
+1901
+1838
+1794
+1815
+1388
+1809
+1920
+1411
+1593
+1676
+1610
+1629
+1512
+1522
+1649
+1740
+1695
+1504
+1856
+1791
+1898
+1661
+1806
+1851

01/main.go

@@ -0,0 +1,88 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"strconv"
+)
+
+func main() {
+	partOne()
+	partTwo()
+}
+
+// [...] they need you to find the two entries that sum to 2020 and then multiply those two numbers together.
+// For example, suppose your expense report contained the following:
+// 1721
+// 979
+// 366
+// 299
+// 675
+// 1456
+// In this list, the two entries that sum to 2020 are 1721 and 299.
+// Multiplying them together produces 1721 * 299 = 514579, so the correct answer is 514579.
+
+func partOne() {
+	f, _ := os.Open("input")
+	reader := bufio.NewReader(f)
+	scanner := bufio.NewScanner(reader)
+
+	numbers := []int{}
+
+	for scanner.Scan() {
+		i, _ := strconv.Atoi(scanner.Text())
+		numbers = append(numbers, i)
+	}
+
+	for i := range numbers {
+		if result := checkTwoSums(numbers[i], numbers[i+1:]); result != 0 {
+			fmt.Println(result)
+			return
+		}
+	}
+}
+
+func checkTwoSums(i int, rest []int) int {
+	for _, j := range rest {
+		if i+j == 2020 {
+			return i * j
+		}
+	}
+	return 0
+}
+
+// Can find three numbers in your expense report that meet the same criteria?
+// Using the above example again, the three entries that sum to 2020 are 979, 366, and 675.
+// Multiplying them together produces the answer, 241861950.
+
+func partTwo() {
+	f, _ := os.Open("input")
+	reader := bufio.NewReader(f)
+	scanner := bufio.NewScanner(reader)
+
+	numbers := []int{}
+
+	for scanner.Scan() {
+		i, _ := strconv.Atoi(scanner.Text())
+		numbers = append(numbers, i)
+	}
+
+	for i := range numbers {
+		for j := range numbers[i+1:] {
+			if result := checkThreeSums(numbers[i], numbers[j], numbers[j+1:]); result != 0 {
+				fmt.Println(result)
+				return
+			}
+		}
+	}
+}
+
+func checkThreeSums(i int, j int, rest []int) int {
+	for _, k := range rest {
+		if i+j+k == 2020 {
+			return i * j * k
+		}
+	}
+	return 0
+}