22 lines
363 B
Python
22 lines
363 B
Python
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import string, itertools
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t = int(input())
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for _ in range(t):
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n = int(input())
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s = input()
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filtered = []
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s = ''.join(i for i, _ in itertools.groupby(s))
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check = True
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for i in string.ascii_uppercase:
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if s.count(i) > 1:
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check = False
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break
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if check:
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print("YES")
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else:
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print("NO")
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