03: part1+2

3/part1.go

@@ -0,0 +1,39 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+)
+
+//const entryBits = 12
+//const entryBits = 5
+
+func main() {
+	zeroes := [entryBits]int{}
+	ones := [entryBits]int{}
+
+	s := bufio.NewScanner(os.Stdin)
+	for s.Scan() {
+		for i, v := range s.Bytes() {
+			if v == '0' {
+				zeroes[i]++
+			} else {
+				ones[i]++
+			}
+		}
+	}
+
+	gamma := 0
+
+	for i := range zeroes {
+		if ones[i] > zeroes[i] {
+			gamma |= 1 << (entryBits - i - 1)
+		}
+	}
+
+
+	epsilon := gamma ^ ((1 << entryBits) - 1)
+
+	fmt.Println(gamma * epsilon)
+}

3/part2.go

@@ -0,0 +1,89 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"strconv"
+)
+
+const entryBits = 12
+//const entryBits = 5
+
+func nthBit(f int, i int) int {
+	a := entryBits - i - 1
+	return f & (1 << a) >> a
+}
+
+type NumberList []int
+
+func (n NumberList) CountBits(index int) (ones int, zeroes int) {
+	for _, num := range n {
+		if nthBit(num, index) == 1 {
+			ones++
+		} else {
+			zeroes++
+		}
+	}
+	return
+}
+
+func (n NumberList) Filter(index int, bit int) NumberList {
+	var res NumberList
+	for _, num := range n {
+		if nthBit(num, index) == bit {
+			res = append(res, num)
+		}
+	}
+	return res
+}
+
+func main() {
+	var numbers NumberList
+
+	s := bufio.NewScanner(os.Stdin)
+	for s.Scan() {
+		value, _ := strconv.ParseInt(s.Text(), 2, 64)
+		numbers = append(numbers, int(value))
+	}
+
+	oxygenNumbers := numbers
+	for i := 0; i < entryBits; i++ {
+		ones, zeroes := oxygenNumbers.CountBits(i)
+
+		var bit int
+		if ones >= zeroes {
+			bit = 1
+		} else {
+			bit = 0
+		}
+
+		//fmt.Println(i, bit, zeroes, ones, len(oxygenNumbers))
+		oxygenNumbers = oxygenNumbers.Filter(i, bit)
+		if len(oxygenNumbers) == 1 {
+			break
+		}
+	}
+	oxygen := oxygenNumbers[0]
+
+	co2Numbers := numbers
+	for i := 0; i < entryBits; i++ {
+		ones, zeroes := co2Numbers.CountBits(i)
+
+		var bit int
+		if ones < zeroes {
+			bit = 1
+		} else {
+			bit = 0
+		}
+
+		//fmt.Println(i, bit, zeroes, ones, len(co2Numbers))
+		co2Numbers = co2Numbers.Filter(i, bit)
+		if len(co2Numbers) == 1 {
+			break
+		}
+	}
+	co2 := co2Numbers[0]
+
+	fmt.Println(oxygen * co2)
+}

3/testinput

@@ -0,0 +1,12 @@
+00100
+11110
+10110
+10111
+10101
+01111
+00111
+11100
+10000
+11001
+00010
+01010