2019 Day 04 Done

2019/day04/main.go

@@ -0,0 +1,60 @@
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"os"
+)
+
+func main() {
+	beg, end := []byte("165432"), []byte("707912")
+	if len(os.Args) == 3 {
+		beg, end = []byte(os.Args[1]), []byte(os.Args[2])
+	}
+	var count int
+	for {
+		if validate(beg) {
+			count++
+		}
+		if bytes.Equal(beg, end) {
+			break
+		}
+		beg = inc(beg)
+	}
+	fmt.Println(count)
+}
+
+func inc(num []byte) []byte {
+	if len(num) == 0 {
+		return []byte{'1'}
+	} else if num[len(num)-1] == '9' {
+		return append(inc(num[:len(num)-1]), '0')
+	} else {
+		num[len(num)-1]++
+	}
+	return num
+}
+
+func validate(num []byte) bool {
+	var dup bool
+	for k := range num {
+		if countSeq(num, k) == 2 {
+			dup = true
+		}
+		if len(num) > k+1 && num[k] > num[k+1] {
+			return false
+		}
+	}
+	return dup
+}
+
+func countSeq(num []byte, idx int) int {
+	ret := 1
+	if len(num) > idx+1 && num[idx+1] == num[idx] {
+		ret += countSeq(num[idx+1:], 0)
+	}
+	if idx >= 1 && num[idx-1] == num[idx] {
+		ret += countSeq(num[:idx], idx-1)
+	}
+	return ret
+}