无重复字母词

Determine if a word or phrase is an isogram.

An isogram (also known as a "non-pattern word") is a word or phrase without a repeating letter, however spaces and hyphens are allowed to appear multiple times.

Examples of isograms:

• lumberjacks
• background
• downstream
• six-year-old

The word isograms, however, is not an isogram, because the s repeats.