Add failing text case and change the logic to pass the test

Author: spring1843

strings/longest_dictionary_word.go

@@ -16,12 +16,12 @@ func LongestDictionaryWordContainingKey(key string, dic []string) string {
 	return longest
 }
 
-// hash turns a string into a number
-// the output for "abc", "acb", "cba" and etc… are all the same.
-func hash(s string) rune {
-	var res rune
-	for _, w := range s {
-		res |= w
+// hash turns a string into a number representing a bitmask of characters
+// the output for "abc", "acb", "cba", "aabc", "aaabbcc" and etc… are all the same.
+func hash(input string) int64 {
+	var res int64
+	for _, char := range input {
+		res |= 1 << (char - 'a')
 	}
 	return res
 }

strings/longest_dictionary_word_test.go

@@ -8,7 +8,7 @@ TestLongestDictionaryWordContainingKey tests solution(s) with the following sign
 	func LongestDictionaryWordContainingKey(key string, dic []string) string
 
 Given a key as string, and a slice of strings containing a dictionary of words, return the longest
-word that contains all letters of the key.
+word that contains all letters of the key. Input will only contain lowercase letters a-z.
 
 For example given "car" and {"rectify", "race", "archeology", "racoon"}, it should return "archeology",
 because "archeology" is the longest word in the given set that contains "c","a",and "r".
@@ -20,10 +20,12 @@ func TestLongestDictionaryWordContainingKey(t *testing.T) {
 		longestWordContainingCharacters string
 	}{
 		{"a", []string{}, ""},
+		{"a", []string{"c"}, ""},
 		{"", []string{"abc"}, "abc"},
 		{"a", []string{"a", "b", "c"}, "a"},
 		{"a", []string{"a", "ba", "c", "cc"}, "ba"},
 		{"a", []string{"a", "baa", "c"}, "baa"},
+		{"abc", []string{"abc", "aabc", "aabbcc", "bbccaaccbbaa"}, "bbccaaccbbaa"},
 		{"abc", []string{"abc", "abcdefghijklmn", "abcdefghijkl", "abcdef", "abcijkl"}, "abcdefghijklmn"},
 		{"car", []string{"rectify", "race", "archeology", "racoon"}, "archeology"},
 	}