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day2/Readme.md

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+--- Day 2: Red-Nosed Reports ---
+Fortunately, the first location The Historians want to search isn't a long walk from the Chief Historian's office.
+
+While the Red-Nosed Reindeer nuclear fusion/fission plant appears to contain no sign of the Chief Historian, the engineers there run up to you as soon as they see you. Apparently, they still talk about the time Rudolph was saved through molecular synthesis from a single electron.
+
+They're quick to add that - since you're already here - they'd really appreciate your help analyzing some unusual data from the Red-Nosed reactor. You turn to check if The Historians are waiting for you, but they seem to have already divided into groups that are currently searching every corner of the facility. You offer to help with the unusual data.
+
+The unusual data (your puzzle input) consists of many reports, one report per line. Each report is a list of numbers called levels that are separated by spaces. For example:
+
+7 6 4 2 1
+1 2 7 8 9
+9 7 6 2 1
+1 3 2 4 5
+8 6 4 4 1
+1 3 6 7 9
+This example data contains six reports each containing five levels.
+
+The engineers are trying to figure out which reports are safe. The Red-Nosed reactor safety systems can only tolerate levels that are either gradually increasing or gradually decreasing. So, a report only counts as safe if both of the following are true:
+
+The levels are either all increasing or all decreasing.
+Any two adjacent levels differ by at least one and at most three.
+In the example above, the reports can be found safe or unsafe by checking those rules:
+
+7 6 4 2 1: Safe because the levels are all decreasing by 1 or 2.
+1 2 7 8 9: Unsafe because 2 7 is an increase of 5.
+9 7 6 2 1: Unsafe because 6 2 is a decrease of 4.
+1 3 2 4 5: Unsafe because 1 3 is increasing but 3 2 is decreasing.
+8 6 4 4 1: Unsafe because 4 4 is neither an increase or a decrease.
+1 3 6 7 9: Safe because the levels are all increasing by 1, 2, or 3.
+So, in this example, 2 reports are safe.
+
+Analyze the unusual data from the engineers. How many reports are safe?
+
+Your puzzle answer was 559.
+
+--- Part Two ---
+The engineers are surprised by the low number of safe reports until they realize they forgot to tell you about the Problem Dampener.
+
+The Problem Dampener is a reactor-mounted module that lets the reactor safety systems tolerate a single bad level in what would otherwise be a safe report. It's like the bad level never happened!
+
+Now, the same rules apply as before, except if removing a single level from an unsafe report would make it safe, the report instead counts as safe.
+
+More of the above example's reports are now safe:
+
+7 6 4 2 1: Safe without removing any level.
+1 2 7 8 9: Unsafe regardless of which level is removed.
+9 7 6 2 1: Unsafe regardless of which level is removed.
+1 3 2 4 5: Safe by removing the second level, 3.
+8 6 4 4 1: Safe by removing the third level, 4.
+1 3 6 7 9: Safe without removing any level.
+Thanks to the Problem Dampener, 4 reports are actually safe!
+
+Update your analysis by handling situations where the Problem Dampener can remove a single level from unsafe reports. How many reports are now safe?
+
+Your puzzle answer was 601.
+
+Both parts of this puzzle are complete! They provide two gold stars: **
+
+At this point, you should return to your Advent calendar and try another puzzle.
+
+If you still want to see it, you can get your puzzle input.
+
+You can also [Share] this puzzle.

day3/Readme.md

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+--- Day 3: Mull It Over ---
+"Our computers are having issues, so I have no idea if we have any Chief Historians in stock! You're welcome to check the warehouse, though," says the mildly flustered shopkeeper at the North Pole Toboggan Rental Shop. The Historians head out to take a look.
+
+The shopkeeper turns to you. "Any chance you can see why our computers are having issues again?"
+
+The computer appears to be trying to run a program, but its memory (your puzzle input) is corrupted. All of the instructions have been jumbled up!
+
+It seems like the goal of the program is just to multiply some numbers. It does that with instructions like mul(X,Y), where X and Y are each 1-3 digit numbers. For instance, mul(44,46) multiplies 44 by 46 to get a result of 2024. Similarly, mul(123,4) would multiply 123 by 4.
+
+However, because the program's memory has been corrupted, there are also many invalid characters that should be ignored, even if they look like part of a mul instruction. Sequences like mul(4*, mul(6,9!, ?(12,34), or mul ( 2 , 4 ) do nothing.
+
+For example, consider the following section of corrupted memory:
+
+xmul(2,4)%&mul[3,7]!@^do_not_mul(5,5)+mul(32,64]then(mul(11,8)mul(8,5))
+Only the four highlighted sections are real mul instructions. Adding up the result of each instruction produces 161 (2*4 + 5*5 + 11*8 + 8*5).
+
+Scan the corrupted memory for uncorrupted mul instructions. What do you get if you add up all of the results of the multiplications?
+
+Your puzzle answer was 192767529.
+
+--- Part Two ---
+As you scan through the corrupted memory, you notice that some of the conditional statements are also still intact. If you handle some of the uncorrupted conditional statements in the program, you might be able to get an even more accurate result.
+
+There are two new instructions you'll need to handle:
+
+The do() instruction enables future mul instructions.
+The don't() instruction disables future mul instructions.
+Only the most recent do() or don't() instruction applies. At the beginning of the program, mul instructions are enabled.
+
+For example:
+
+xmul(2,4)&mul[3,7]!^don't()_mul(5,5)+mul(32,64](mul(11,8)undo()?mul(8,5))
+This corrupted memory is similar to the example from before, but this time the mul(5,5) and mul(11,8) instructions are disabled because there is a don't() instruction before them. The other mul instructions function normally, including the one at the end that gets re-enabled by a do() instruction.
+
+This time, the sum of the results is 48 (2*4 + 8*5).
+
+Handle the new instructions; what do you get if you add up all of the results of just the enabled multiplications?
+
+Your puzzle answer was 104083373.
+
+Both parts of this puzzle are complete! They provide two gold stars: **
+
+At this point, you should return to your Advent calendar and try another puzzle.
+
+If you still want to see it, you can get your puzzle input.
+
+You can also [Share] this puzzle.