From fc806e89614e6cb0f17b6699799325b5de9677fb Mon Sep 17 00:00:00 2001
From: Ettore Dreucci <ettore.dreucci@gmail.com>
Date: Wed, 4 Dec 2019 17:30:55 +0100
Subject: [PATCH] 2019. Day 4. Part 1

Signed-off-by: Ettore Dreucci <ettore.dreucci@gmail.com>
---
 2019/day_04/day_04.go | 48 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)
 create mode 100644 2019/day_04/day_04.go

diff --git a/2019/day_04/day_04.go b/2019/day_04/day_04.go
new file mode 100644
index 0000000..38e1049
--- /dev/null
+++ b/2019/day_04/day_04.go
@@ -0,0 +1,48 @@
+package main
+
+import "fmt"
+
+const (
+	min = 130254
+	max = 678275
+)
+
+func intToSlice(n int) []int {
+	s := make([]int, 0)
+	for n != 0 {
+		r := n % 10
+		n = n / 10
+		s = append([]int{r}, s...)
+	}
+	return s
+}
+
+func twoEqualAdjacentDigits(pwd []int) bool {
+	for i, digit := range pwd {
+		if i < len(pwd)-1 && digit == pwd[i+1] {
+			return true
+		}
+	}
+	return false
+}
+
+func increasingDigits(pwd []int) bool {
+	for i, digit := range pwd {
+		if i < len(pwd)-1 && digit > pwd[i+1] {
+			return false
+		}
+	}
+	return true
+}
+
+func main() {
+	// Part 1:
+	count := 0
+	for i := min; i < max; i++ {
+		pwd := intToSlice(i)
+		if twoEqualAdjacentDigits(pwd) && increasingDigits(pwd) {
+			count++
+		}
+	}
+	fmt.Printf("Part 1: %d\n", count)
+}