day 7 simplify: process input from front instead of back

vaskoz · Apr 3, 2019 · 275ac7b · 275ac7b
1 parent 5a02664
commit 275ac7b
Showing 1 changed file with 4 additions and 6 deletions.
diff --git a/day7/problem.go b/day7/problem.go
@@ -3,15 +3,13 @@ package day7
 // NumberOfDecodings calculates the number of possible decodings where
 // letters are encoding as a=1, b=2 ... z=26
 func NumberOfDecodings(str string) int {
-	if length := len(str); length == 0 || length == 1 {
+	if length := len(str); length < 2 {
 		return 1
 	}
 	var count int
-	if last := str[len(str)-1]; last > '0' && last <= '9' {
-		count = NumberOfDecodings(str[:len(str)-1])
-	}
-	if second := str[len(str)-2]; second == '1' || second == '2' && str[len(str)-1] < '7' {
-		count += NumberOfDecodings(str[:len(str)-2])
+	if first := str[0]; first == '1' || (first == '2' && str[1] < '7') {
+		count = NumberOfDecodings(str[2:])
 	}
+	count += NumberOfDecodings(str[1:])
 	return count
 }