Initial commit.

day1/input

@@ -0,0 +1,200 @@
+1977
+1802
+1856
+1309
+2003
+1854
+1898
+1862
+1857
+542
+1616
+1599
+1628
+1511
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+1202
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+1598
+1926
+1865
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+1578
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+1313
+1997
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+1971
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+1884
+1956
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+1689
+1726
+1217
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+1536
+1213
+1867
+1304
+2010
+1503
+1665
+1361
+814
+2007
+1430
+1625
+1958
+860
+1799
+1942
+1876
+1772
+1198
+1221
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+21
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+1321
+1119
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+1834
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+1505
+1656
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+1982
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+1849

day1/part1/test.go

@@ -0,0 +1,36 @@
+package main
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"io/ioutil"
+	"strconv"
+	"strings"
+)
+
+func main() {
+	nums := []int{}
+	f, err := ioutil.ReadFile("input")
+	if err != nil {
+		panic(err)
+	}
+	reader := bufio.NewReader(bytes.NewReader(f))
+	for {
+		line, err := reader.ReadString('\n')
+		if err != nil {
+			break
+		}
+		i, err := strconv.Atoi(strings.TrimSpace(line))
+		if err != nil {
+			panic(err)
+		}
+		for _, num := range nums {
+			if i+num == 2020 {
+				fmt.Printf("%d", i*num)
+				return
+			}
+		}
+		nums = append(nums, i)
+	}
+}

day1/part2/test2.go

@@ -0,0 +1,48 @@
+package main
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"io/ioutil"
+	"strconv"
+	"strings"
+)
+
+func main() {
+	nums := []int{}
+	f, err := ioutil.ReadFile("input")
+	if err != nil {
+		panic(err)
+	}
+	reader := bufio.NewReader(bytes.NewReader(f))
+	for {
+		line, err := reader.ReadString('\n')
+		if err != nil {
+			break
+		}
+		line = strings.TrimSpace(line)
+		if len(line) == 0 {
+			continue
+		}
+		i, err := strconv.Atoi(line)
+		if err != nil {
+			panic(err)
+		}
+		nums = append(nums, i)
+	}
+
+	max := len(nums)
+
+	for p1 := 0; p1 < max; p1++ {
+		for p2 := 0; p2 < max; p2++ {
+			for p3 := 0; p3 < max; p3++ {
+				sum := nums[p1] + nums[p2] + nums[p3]
+				if sum == 2020 {
+					fmt.Printf("%d", nums[p1]*nums[p2]*nums[p3])
+					return
+				}
+			}
+		}
+	}
+}

day2/part1/main.go

@@ -0,0 +1,44 @@
+package main
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"io/ioutil"
+	"log"
+)
+
+func main() {
+	f, err := ioutil.ReadFile("input")
+	if err != nil {
+		panic(err)
+	}
+	reader := bufio.NewReader(bytes.NewReader(f))
+	var valid int
+	for {
+		line, err := reader.ReadString('\n')
+		if err != nil {
+			break
+		}
+		var pw string
+		var min, max int
+		var char rune
+		n, err := fmt.Sscanf(line, "%d-%d %c: %s", &min, &max, &char, &pw)
+		if err != nil {
+			panic(err)
+		}
+		if n != 4 {
+			panic("mismatched Scanf")
+		}
+		var count int
+		for _, currentChar := range pw {
+			if currentChar == char {
+				count++
+			}
+		}
+		if count >= min && count <= max {
+			valid++
+		}
+	}
+	log.Printf("%d valid entries", valid)
+}

day2/part2/main.go

@@ -0,0 +1,43 @@
+package main
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"io/ioutil"
+	"log"
+)
+
+func main() {
+	f, err := ioutil.ReadFile("input")
+	if err != nil {
+		panic(err)
+	}
+	reader := bufio.NewReader(bytes.NewReader(f))
+	var valid int
+	for {
+		line, err := reader.ReadString('\n')
+		if err != nil {
+			break
+		}
+		var pw string
+		var min, max int
+		var char rune
+		n, err := fmt.Sscanf(line, "%d-%d %c: %s", &min, &max, &char, &pw)
+		if err != nil {
+			panic(err)
+		}
+		if n != 4 {
+			panic("mismatched Scanf")
+		}
+		min--
+		max--
+		has1 := rune(pw[min]) == char
+		has2 := rune(pw[max]) == char
+		if has1 == has2 { // both false or both true
+			continue
+		}
+		valid++
+	}
+	log.Printf("%d valid entries", valid)
+}

go.mod

@@ -0,0 +1,3 @@
+module github.com/icedream/adventofcode-2020
+
+go 1.15