Added the first days

2021/03/first.go

@@ -0,0 +1,42 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"log"
+	"os"
+)
+
+func main() {
+	f, err := os.Open("input")
+	if err != nil {
+		log.Fatalf("%+v", err)
+	}
+	defer f.Close()
+
+	scanner := bufio.NewScanner(f)
+	scanner.Split(bufio.ScanLines)
+
+	bits := make([]int, 12)
+	for scanner.Scan() {
+		num := scanner.Text()
+		for n := 0; n < 12; n++ {
+			if num[n] == '1' {
+				bits[n]++
+			}
+		}
+	}
+
+	gamma := 0
+	epsilon := 0
+	for n := 0; n < 12; n++ {
+		gamma *= 2
+		epsilon *= 2
+		if bits[n] > 500 {
+			gamma++
+		} else {
+			epsilon++
+		}
+	}
+	fmt.Println(gamma * epsilon)
+}

2021/03/second.go

@@ -0,0 +1,96 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"log"
+	"os"
+)
+
+func findBitCount(data []string) []int {
+	bits := make([]int, 12)
+	for _, line := range data {
+		for n := 0; n < 12; n++ {
+			if line[n] == '1' {
+				bits[n]++
+			}
+		}
+	}
+	return bits
+}
+
+func main() {
+	f, err := os.Open("input")
+	if err != nil {
+		log.Fatalf("%+v", err)
+	}
+	defer f.Close()
+
+	scanner := bufio.NewScanner(f)
+	scanner.Split(bufio.ScanLines)
+
+	data := make([]string, 0)
+	for scanner.Scan() {
+		data = append(data, scanner.Text())
+	}
+
+	datacsr := make([]string, len(data))
+	copy(datacsr, data)
+
+	var ogr int
+	for n := 0; n < 12; n++ {
+		if len(data) == 1 {
+			break
+		}
+		bits := findBitCount(data)
+		var i byte
+		if 2*bits[n] >= len(data) {
+			i = '1'
+		} else {
+			i = '0'
+		}
+		newdata := make([]string, 0)
+		for j := 0; j < len(data); j++ {
+			if data[j][n] == i {
+				newdata = append(newdata, data[j])
+			}
+		}
+		data = newdata
+	}
+	for n := 0; n < 12; n++ {
+		ogr *= 2
+		if data[0][n] == '1' {
+			ogr++
+		}
+	}
+
+	data = datacsr
+	var csr int
+	for n := 0; n < 12; n++ {
+		if len(data) == 1 {
+			break
+		}
+		bits := findBitCount(data)
+		var i byte
+		if 2*bits[n] < len(data) {
+			i = '1'
+		} else {
+			i = '0'
+		}
+		newdata := make([]string, 0)
+		for j := 0; j < len(data); j++ {
+			if data[j][n] == i {
+				newdata = append(newdata, data[j])
+			}
+		}
+		data = newdata
+	}
+	for n := 0; n < 12; n++ {
+		csr *= 2
+		if data[0][n] == '1' {
+			csr++
+		}
+	}
+
+	fmt.Println(ogr * csr)
+}