practice for loop

Author: fanzipei

17_letter_combinations_of_a_phone_number.scala

@@ -0,0 +1,8 @@
+object Solution {
+    def letterCombinations(digits: String): List[String] = {
+        if (digits.isEmpty) List() else{
+            val keyMap = Map('2' -> "abc", '3' -> "def", '4' -> "ghi", '5' -> "jkl", '6' -> "mno", '7' -> "pqrs", '8' -> "tuv", '9' -> "wxyz")
+            digits.map(keyMap).foldLeft(List(""))(for {a <- _; b <- _} yield (a + b))
+        }
+    }
+}