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36 changes: 36 additions & 0 deletions data_structures/stacks/lexicographical_numbers.py
Original file line number Diff line number Diff line change
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def lexical_order(max_number: int) -> str:
"""
Generate numbers in lexical order from 1 to max_number.

>>> lexical_order(13)
'1 10 11 12 13 2 3 4 5 6 7 8 9'
>>> lexical_order(1)
'1'
>>> lexical_order(20)
'1 10 11 12 13 14 15 16 17 18 19 2 20 3 4 5 6 7 8 9'
>>> lexical_order(25)
'1 10 11 12 13 14 15 16 17 18 19 2 20 21 22 23 24 25 3 4 5 6 7 8 9'
"""

ans = []
stack = [1]

while stack:
num = stack.pop()
if num > max_number:
continue

ans.append(str(num))
if (num % 10) != 9:
stack.append(num + 1)

stack.append(num * 10)

return " ".join(ans)


if __name__ == "__main__":
from doctest import testmod

testmod()
print(f"Numbers from 1 to 25 in lexical order: {lexical_order(25)}")