31 lines
1.5 KiB
Plaintext
31 lines
1.5 KiB
Plaintext
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--- Day 4: Secure Container ---
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You arrive at the Venus fuel depot only to discover it's protected by a password. The Elves had written the password on a sticky note, but someone threw it out.
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However, they do remember a few key facts about the password:
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It is a six-digit number.
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The value is within the range given in your puzzle input.
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Two adjacent digits are the same (like 22 in 122345).
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Going from left to right, the digits never decrease; they only ever increase or stay the same (like 111123 or 135679).
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Other than the range rule, the following are true:
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111111 meets these criteria (double 11, never decreases).
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223450 does not meet these criteria (decreasing pair of digits 50).
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123789 does not meet these criteria (no double).
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How many different passwords within the range given in your puzzle input meet these criteria?
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--- Part Two ---
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An Elf just remembered one more important detail: the two adjacent matching digits are not part of a larger group of matching digits.
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Given this additional criterion, but still ignoring the range rule, the following are now true:
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112233 meets these criteria because the digits never decrease and all repeated digits are exactly two digits long.
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123444 no longer meets the criteria (the repeated 44 is part of a larger group of 444).
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111122 meets the criteria (even though 1 is repeated more than twice, it still contains a double 22).
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How many different passwords within the range given in your puzzle input meet all of the criteria?
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