Merge 9bf72ea into 66d338e

README.md

@@ -462,5 +462,6 @@ problems from
 * [Day 463](https://github.com/vaskoz/dailycodingproblem-go/issues/937)
 * [Day 464](https://github.com/vaskoz/dailycodingproblem-go/issues/935)
 * [Day 465](https://github.com/vaskoz/dailycodingproblem-go/issues/933)
+* [Day 472](https://github.com/vaskoz/dailycodingproblem-go/issues/941)
 * [Day 473](https://github.com/vaskoz/dailycodingproblem-go/issues/939)
 

day472/problem.go

@@ -0,0 +1,17 @@
+package day472
+
+// 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 < 2 {
+		return 1
+	}
+
+	count := 0
+
+	if first := str[0]; first == '1' || (first == '2' && str[1] < '7') {
+		count = NumberOfDecodings(str[2:])
+	}
+
+	return count + NumberOfDecodings(str[1:])
+}

day472/problem_test.go

@@ -0,0 +1,33 @@
+package day472
+
+import "testing"
+
+// nolint
+var testcases = []struct {
+	input    string
+	expected int
+}{
+	{"111", 3},
+	{"1111", 5},
+	{"2626", 4},
+	{"1234", 3},
+	{"1111127", 13},
+}
+
+func TestNumberOfDecodings(t *testing.T) {
+	t.Parallel()
+
+	for _, tc := range testcases {
+		if result := NumberOfDecodings(tc.input); result != tc.expected {
+			t.Errorf("For input %v, expected %v but got %v", tc.input, tc.expected, result)
+		}
+	}
+}
+
+func BenchmarkNumberOfDecodings(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		for _, tc := range testcases {
+			NumberOfDecodings(tc.input)
+		}
+	}
+}