Add: Decrypt String from Alphabet to Integer Mapping

Author: Shuo

Diff for: problems/decrypt-string-from-alphabet-to-integer-mapping/decrypt_string_from_alphabet_to_integer_mapping.go

@@ -0,0 +1,16 @@
+package problem1309
+
+func freqAlphabets(s string) string {
+	l := len(s)
+	ans, head := make([]byte, l), l-1
+	for i := l - 1; i >= 0; i-- {
+		if s[i] == '#' {
+			ans[head] = 'a' + (s[i-1] - '1') + (s[i-2]-'0')*10
+			i -= 2
+		} else {
+			ans[head] = 'a' + (s[i] - '1')
+		}
+		head--
+	}
+	return string(ans[head+1:])
+}

Diff for: problems/decrypt-string-from-alphabet-to-integer-mapping/decrypt_string_from_alphabet_to_integer_mapping_test.go

@@ -0,0 +1,31 @@
+package problem1309
+
+import "testing"
+
+type testType struct {
+	in   string
+	want string
+}
+
+func TestFreqAlphabets(t *testing.T) {
+	tests := [...]testType{
+		{
+			in:   "10#11#12",
+			want: "jkab",
+		},
+		{
+			in:   "1326#",
+			want: "acz",
+		},
+		{
+			in:   "12345678910#11#12#13#14#15#16#17#18#19#20#21#22#23#24#25#26#",
+			want: "abcdefghijklmnopqrstuvwxyz",
+		},
+	}
+	for _, tt := range tests {
+		got := freqAlphabets(tt.in)
+		if got != tt.want {
+			t.Fatalf("in: %v, got: %v, want: %v", tt.in, got, tt.want)
+		}
+	}
+}