Day Four

1 files changed, 68 insertions, 0 deletions

diff --git a/four.go b/four.go
new file mode 100644
index 0000000..7c901dc
--- /dev/null
+++ b/four.go
@@ -0,0 +1,68 @@
+package main
+
+import (
+	"fmt"
+	"io/ioutil"
+	"math"
+	"os"
+	"strconv"
+)
+
+func main() {
+	smallest, largest, total, details := -1, -1, 0, 0
+	if len(os.Args) < 2 {
+		panic("runtime error: missing operand")
+	}
+	file, err := ioutil.ReadFile(os.Args[1])
+	if err != nil {
+		panic(err)
+	}
+	for i := 0; i < len(file); i++ {
+		if string(file[i]) == "-" {
+			smallest, err = strconv.Atoi(string(file[0:i]))
+			if err != nil {
+				panic(err)
+			}
+			largest, err = strconv.Atoi(string(file[i+1 : len(file)-1]))
+			if err != nil {
+				panic(err)
+			}
+			break
+		}
+	}
+
+	for i := smallest; i <= largest; i++ {
+		if criteria(i, false) {
+			total++
+		}
+		if criteria(i, true) {
+			details++
+		}
+	}
+	fmt.Println(total)
+	fmt.Println(details)
+}
+
+func criteria(password int, stage bool) bool {
+	prev := 0
+	for i := 0; i < 6; i++ {
+		if password/int(math.Pow(10, float64(5-i)))%10 < prev {
+			return false
+		}
+		prev = password / int(math.Pow(10, float64(5-i))) % 10
+	}
+	pascii := strconv.Itoa(password)
+	for i := 0; i < len(pascii)-1; i++ {
+		if string(pascii[i]) == string(pascii[i+1]) {
+			if !(len(pascii)-i > 2 && string(pascii[i]) == string(pascii[i+2])) {
+				if !stage { // Gross hack
+					return true
+				}
+				if !(i > 0 && string(pascii[i]) == string(pascii[i-1])) {
+					return true
+				}
+			}
+		}
+	}
+	return false
+}