Actual solution for day 16!

README.md

@@ -170,7 +170,6 @@ The total risk of the least risky path is 2864
 ```sh
 $ ./aoc2021 --sixteen
 The solution for "sixteen" is:
-sixteen part 1 answer for bits
+The sum of the version numbers is 1012
-sixteen part 2 answer for bits
+The output of the encoded input is 2223947372407
 ```
-

sixteen/bits.go

@@ -50,6 +50,87 @@ func (p *packet) versionSum() int {
 	return sum
 }
 
+func (p *packet) sum() int {
+	sum := 0
+	for _, p := range p.subpackets {
+		sum += p.value()
+	}
+	return sum
+}
+
+func (p *packet) product() int {
+	product := 1
+	for _, p := range p.subpackets {
+		product *= p.value()
+	}
+	return product
+}
+
+func (p *packet) min() int {
+	min := 0
+	for i, p := range p.subpackets {
+		if i == 0 || p.content < min {
+			min = p.value()
+		}
+	}
+	return min
+}
+
+func (p *packet) max() int {
+	max := 0
+	for i, p := range p.subpackets {
+		if i == 0 || p.content > max {
+			max = p.value()
+		}
+	}
+	return max
+}
+
+func (p *packet) greaterThan() int {
+	result := 0
+	if p.subpackets[0].value() > p.subpackets[1].value() {
+		result = 1
+	}
+	return result
+}
+
+func (p *packet) lessThan() int {
+	result := 0
+	if p.subpackets[0].value() < p.subpackets[1].value() {
+		result = 1
+	}
+	return result
+}
+
+func (p *packet) equalTo() int {
+	result := 0
+	if p.subpackets[0].value() == p.subpackets[1].value() {
+		result = 1
+	}
+	return result
+}
+
+func (p *packet) value() int {
+	switch p.typeID {
+	case 0:
+		return p.sum()
+	case 1:
+		return p.product()
+	case 2:
+		return p.min()
+	case 3:
+		return p.max()
+	case 5:
+		return p.greaterThan()
+	case 6:
+		return p.lessThan()
+	case 7:
+		return p.equalTo()
+	}
+
+	return p.content
+}
+
 func hexToBinary(input string) string {
 	output := ""
 	for _, r := range input {
@@ -124,7 +205,11 @@ func parsePackets(input string) []packet {
 		default:
 			l := 0
 			p.subpackets, l = parseOperator(remaining[6:])
-			remaining = remaining[l+7:]
+			if len(remaining) == l+6 {
+				remaining = ""
+			} else {
+				remaining = remaining[l+6:]
+			}
 		}
 
 		packets = append(packets, p)
@@ -146,16 +231,21 @@ func parseNPackets(input string, count int) ([]packet, int) {
 			typeID:  typeID,
 		}
 
+		parsedLength := 0
 		switch p.typeID {
 		case literalType:
-			value, length := parseLiteral(remaining[6:])
+			value := 0
+			value, parsedLength = parseLiteral(remaining[6:])
 			p.content = value
-			p.packet = remaining[:length+6]
+			p.packet = remaining[:parsedLength+6]
-			remaining = remaining[length+6:]
 		default:
-			l := 0
+			p.subpackets, parsedLength = parseOperator(remaining[6:])
-			p.subpackets, l = parseOperator(remaining[6:])
+		}
-			remaining = remaining[l+7:]
+
+		if len(remaining) == parsedLength+6 {
+			remaining = ""
+		} else {
+			remaining = remaining[parsedLength+6:]
 		}
 
 		packets = append(packets, p)
@@ -165,7 +255,7 @@ func parseNPackets(input string, count int) ([]packet, int) {
 }
 
 func parseOperator(input string) ([]packet, int) {
-	length := 0
+	length := 1
 	subPackets := []packet{}
 	var lType int
 	var remainder string
@@ -179,12 +269,12 @@ func parseOperator(input string) ([]packet, int) {
 		lengthBits, _ := strconv.ParseInt(string(remainder[:15]), 2, 64)
 		subs := parsePackets(remainder[15 : 15+lengthBits])
 		subPackets = append(subPackets, subs...)
-		length = 15 + int(lengthBits)
+		length += 15 + int(lengthBits)
 	case lengthType11:
 		lengthBits, _ := strconv.ParseInt(string(remainder[:11]), 2, 64)
 		subs, l := parseNPackets(remainder[11:], int(lengthBits))
 		subPackets = append(subPackets, subs...)
-		length = l
+		length += 11 + l
 	}
 
 	return subPackets, length

sixteen/bits_test.go

@@ -1,6 +1,9 @@
 package sixteen
 
-import "testing"
+import (
+	"fmt"
+	"testing"
+)
 
 func Test_hex(t *testing.T) {
 	original := "8A004A801A8002F478"
@@ -50,7 +53,7 @@ func Test_hex4(t *testing.T) {
 
 	if vSum != expected {
 		t.Logf("Expected %d, found %d", expected, vSum)
-		// t.Fail()
+		t.Fail()
 	}
 }
 
@@ -126,7 +129,7 @@ func Test_operator2(t *testing.T) {
 	}
 
 	if b.subpackets[1].content != 2 {
-	t.Logf("Expected second packet to be 2, found %d", b.subpackets[2].content)
+		t.Logf("Expected second packet to be 2, found %d", b.subpackets[2].content)
 		t.Fail()
 	}
 
@@ -135,3 +138,121 @@ func Test_operator2(t *testing.T) {
 		t.Fail()
 	}
 }
+
+func Test_sum(t *testing.T) {
+	original := "C200B40A82"
+	expected := 3
+
+	p := parseHex(original)
+	fmt.Println(p)
+	v := p.value()
+
+	if v != expected {
+		t.Logf("Expected %d, found %d", expected, v)
+		t.Fail()
+	}
+}
+
+func Test_product(t *testing.T) {
+	original := "04005AC33890"
+	expected := 54
+
+	p := parseHex(original)
+	v := p.value()
+
+	if v != expected {
+		t.Logf("Expected %d, found %d", expected, v)
+		t.Fail()
+	}
+}
+
+func Test_min(t *testing.T) {
+	original := "880086C3E88112"
+	expected := 7
+
+	p := parseHex(original)
+	v := p.value()
+
+	if v != expected {
+		t.Logf("Expected %d, found %d", expected, v)
+		t.Fail()
+	}
+}
+
+func Test_max(t *testing.T) {
+	original := "CE00C43D881120"
+	expected := 9
+
+	p := parseHex(original)
+	v := p.value()
+
+	if v != expected {
+		t.Logf("Expected %d, found %d", expected, v)
+		t.Fail()
+	}
+}
+
+func Test_less(t *testing.T) {
+	original := "D8005AC2A8F0"
+	expected := 1
+
+	p := parseHex(original)
+	v := p.value()
+
+	if v != expected {
+		t.Logf("Expected %d, found %d", expected, v)
+		t.Fail()
+	}
+}
+
+func Test_more(t *testing.T) {
+	original := "F600BC2D8F"
+	expected := 0
+
+	p := parseHex(original)
+	v := p.value()
+
+	if v != expected {
+		t.Logf("Expected %d, found %d", expected, v)
+		t.Fail()
+	}
+}
+
+func Test_equal(t *testing.T) {
+	original := "9C005AC2F8F0"
+	expected := 0
+
+	p := parseHex(original)
+	v := p.value()
+
+	if v != expected {
+		t.Logf("Expected %d, found %d", expected, v)
+		t.Fail()
+	}
+}
+
+func Test_combo(t *testing.T) {
+	original := "9C0141080250320F1802104A08"
+	expected := 1
+
+	p := parseHex(original)
+	v := p.value()
+
+	if v != expected {
+		t.Logf("Expected %d, found %d", expected, v)
+		t.Fail()
+	}
+}
+
+func Test_input(t *testing.T) {
+	expected := 531986792411
+
+	p := load("input.txt")
+
+	v := p.value()
+
+	if v == expected {
+		t.Logf("Expected to not get %d, got %d", expected, v)
+		t.Fail()
+	}
+}

sixteen/main.go

@@ -3,23 +3,22 @@ package sixteen
 import "fmt"
 
 type Sixteen struct {
-	bits packet
+	packet packet
 }
 
 func Init(filepath string) *Sixteen {
 	sixteen := &Sixteen{
-		bits: packet{},
+		packet: packet{},
 	}
 
-	sixteen.bits = load(filepath)
+	sixteen.packet = load(filepath)
 	return sixteen
 }
 
 func (d *Sixteen) Answer() string {
-	return fmt.Sprintf("The sum of the version numbers is %d", d.bits.versionSum())
+	return fmt.Sprintf("The sum of the version numbers is %d", d.packet.versionSum())
 }
 
 func (d *Sixteen) FollowUp() string {
-	return "sixteen part 2 answer for bits"
+	return fmt.Sprintf("The output of the encoded input is %d", d.packet.value())
 }
-