From bc8ebae440dfab6f1ffdc7fccea5158c3de5784a Mon Sep 17 00:00:00 2001
From: Parnic <github@parnic.com>
Date: Thu, 9 Jun 2022 08:23:34 -0500
Subject: [PATCH] Day 4 solution

Plenty of room for optimization here, but it's enough for my needs for now.
---
 days/04.go     | 116 +++++++++++++++++++++++++++++++++++++++++++++++++
 inputs/04p.txt |   1 +
 main.go        |   1 +
 3 files changed, 118 insertions(+)
 create mode 100644 days/04.go
 create mode 100644 inputs/04p.txt

diff --git a/days/04.go b/days/04.go
new file mode 100644
index 0000000..3b3e333
--- /dev/null
+++ b/days/04.go
@@ -0,0 +1,116 @@
+package days
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+
+	"parnic.com/aoc2019/utilities"
+)
+
+type Day04 struct {
+	max int
+	min int
+}
+
+func (d *Day04) Parse() {
+	contents := utilities.GetStringContents("04p")
+	vals := strings.Split(contents, "-")
+	d.min, _ = strconv.Atoi(vals[0])
+	d.max, _ = strconv.Atoi(vals[1])
+
+	d.test()
+}
+
+func (d Day04) Num() int {
+	return 4
+}
+
+func (d Day04) test() {
+	if !d.isValidP2(112233) {
+		panic("112233")
+	}
+	if d.isValidP2(123444) {
+		panic("123444")
+	}
+	if !d.isValidP2(111122) {
+		panic("111122")
+	}
+	if !d.isValidP2(112222) {
+		panic("112222")
+	}
+}
+
+func (d Day04) isValidP1(num int) bool {
+	// if num < d.min || num > d.max {
+	// 	return false
+	// }
+
+	numStr := strconv.Itoa(num)
+	lastNum := -1
+	for _, ch := range numStr {
+		thisNum, _ := strconv.Atoi(string(ch))
+		if lastNum > -1 && thisNum < lastNum {
+			return false
+		}
+		lastNum = thisNum
+	}
+
+	foundDouble := false
+	for idx := range numStr {
+		if idx == 0 {
+			continue
+		}
+		if numStr[idx-1] == numStr[idx] {
+			foundDouble = true
+			break
+		}
+	}
+
+	return foundDouble
+}
+
+func (d Day04) isValidP2(num int) bool {
+	if !d.isValidP1(num) {
+		return false
+	}
+
+	numStr := strconv.Itoa(num)
+	for i := 0; i < len(numStr); i++ {
+		consec := 1
+		for j := i + 1; j < len(numStr) && numStr[j] == numStr[i]; j++ {
+			consec++
+			i = j
+		}
+		if consec == 2 {
+			return true
+		}
+	}
+
+	return false
+}
+
+// these could be sped up quite a bit by intelligently jumping to the
+// next valid number when encountering an invalid one, rather than
+// simply incrementing by 1
+func (d *Day04) Part1() string {
+	numValid := 0
+	for x := d.min; x <= d.max; x++ {
+		if d.isValidP1(x) {
+			numValid++
+		}
+	}
+
+	return fmt.Sprintf("Total valid passwords: %s%d%s", utilities.TextBold, numValid, utilities.TextReset)
+}
+
+func (d *Day04) Part2() string {
+	numValid := 0
+	for x := d.min; x <= d.max; x++ {
+		if d.isValidP2(x) {
+			numValid++
+		}
+	}
+
+	return fmt.Sprintf("Total valid passwords: %s%d%s", utilities.TextBold, numValid, utilities.TextReset)
+}
diff --git a/inputs/04p.txt b/inputs/04p.txt
new file mode 100644
index 0000000..ce5f198
--- /dev/null
+++ b/inputs/04p.txt
@@ -0,0 +1 @@
+147981-691423
\ No newline at end of file
diff --git a/main.go b/main.go
index ffa2ec4..9e379f2 100644
--- a/main.go
+++ b/main.go
@@ -28,6 +28,7 @@ var dayMap = []day{
 	&days.Day01{},
 	&days.Day02{},
 	&days.Day03{},
+	&days.Day04{},
 }
 
 func main() {