The challenge
An isogram is a word that has no repeating letters, consecutive or non-consecutive. Implement a function that determines whether a string that contains only letters is an isogram. Assume the empty string is an isogram. Ignore letter case.
is_isogram("Dermatoglyphics" ) == true
is_isogram("aba" ) == false
is_isogram("moOse" ) == false # -- ignore letter case
Test cases
Test.assert_equals(is_isogram("Dermatoglyphics"), True )
Test.assert_equals(is_isogram("isogram"), True )
Test.assert_equals(is_isogram("aba"), False, "same chars may not be adjacent" )
Test.assert_equals(is_isogram("moOse"), False, "same chars may not be same case" )
Test.assert_equals(is_isogram("isIsogram"), False )
Test.assert_equals(is_isogram(""), True, "an empty string is a valid isogram" )
The solution in Python
First pass, using a dictionary (dict):
def is_isogram(string):
# if not a Str then return False
if type(string) is not str:
return False
# if empty then return True
if len(string)==0:
return True
# store characters
db = {}
# loop through the string, but lowercase it first
for char in string.lower():
# if it's already been seen, then return False
if char in db:
return False
else:
# otherwise add to the db
db[char] = 1
# return True if not failed
return True
Make it a bit more efficient by using a set:
def is_isogram(string):
# if not a Str then return False
if type(string) is not str:
return False
# if empty then return True
if len(string)==0:
return True
# store characters
db = set()
# loop through the string, but lowercase it first
for char in string.lower():
# if it's already been seen, then return False
if char in db:
return False
else:
# otherwise add to the db
db.append(char)
# return True if not failed
return True
