From: Neil Smith Date: Sun, 10 Dec 2017 12:35:44 +0000 (+0000) Subject: Added some problem descriptions X-Git-Url: https://git.njae.me.uk/?a=commitdiff_plain;h=369a38f0ba07005a492c7d2286581c665d6e1239;p=advent-of-code-17.git Added some problem descriptions --- diff --git a/problems/day07.html b/problems/day07.html new file mode 100644 index 0000000..a32e8ea --- /dev/null +++ b/problems/day07.html @@ -0,0 +1,181 @@ + + + + +Day 7 - Advent of Code 2017 + + + + + + + +

Advent of Code

Neil Smith (AoC++) 18*

   var y=2017;

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--- Day 7: Recursive Circus ---

Wandering further through the circuits of the computer, you come upon a tower of programs that have gotten themselves into a bit of trouble. A recursive algorithm has gotten out of hand, and now they're balanced precariously in a large tower.

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One program at the bottom supports the entire tower. It's holding a large disc, and on the disc are balanced several more sub-towers. At the bottom of these sub-towers, standing on the bottom disc, are other programs, each holding their own disc, and so on. At the very tops of these sub-sub-sub-...-towers, many programs stand simply keeping the disc below them balanced but with no disc of their own.

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You offer to help, but first you need to understand the structure of these towers. You ask each program to yell out their name, their weight, and (if they're holding a disc) the names of the programs immediately above them balancing on that disc. You write this information down (your puzzle input). Unfortunately, in their panic, they don't do this in an orderly fashion; by the time you're done, you're not sure which program gave which information.

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For example, if your list is the following:

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pbga (66)
+xhth (57)
+ebii (61)
+havc (66)
+ktlj (57)
+fwft (72) -> ktlj, cntj, xhth
+qoyq (66)
+padx (45) -> pbga, havc, qoyq
+tknk (41) -> ugml, padx, fwft
+jptl (61)
+ugml (68) -> gyxo, ebii, jptl
+gyxo (61)
+cntj (57)
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...then you would be able to recreate the structure of the towers that looks like this:

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                gyxo
+              /     
+         ugml - ebii
+       /      \     
+      |         jptl
+      |        
+      |         pbga
+     /        /
+tknk --- padx - havc
+     \        \
+      |         qoyq
+      |             
+      |         ktlj
+       \      /     
+         fwft - cntj
+              \     
+                xhth
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In this example, tknk is at the bottom of the tower (the bottom program), and is holding up ugml, padx, and fwft. Those programs are, in turn, holding up other programs; in this example, none of those programs are holding up any other programs, and are all the tops of their own towers. (The actual tower balancing in front of you is much larger.)

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Before you're ready to help them, you need to make sure your information is correct. What is the name of the bottom program?

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Your puzzle answer was vtzay.

--- Part Two ---

The programs explain the situation: they can't get down. Rather, they could get down, if they weren't expending all of their energy trying to keep the tower balanced. Apparently, one program has the wrong weight, and until it's fixed, they're stuck here.

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For any program holding a disc, each program standing on that disc forms a sub-tower. Each of those sub-towers are supposed to be the same weight, or the disc itself isn't balanced. The weight of a tower is the sum of the weights of the programs in that tower.

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In the example above, this means that for ugml's disc to be balanced, gyxo, ebii, and jptl must all have the same weight, and they do: 61.

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However, for tknk to be balanced, each of the programs standing on its disc and all programs above it must each match. This means that the following sums must all be the same:

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  • ugml + (gyxo + ebii + jptl) = 68 + (61 + 61 + 61) = 251
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  • padx + (pbga + havc + qoyq) = 45 + (66 + 66 + 66) = 243
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  • fwft + (ktlj + cntj + xhth) = 72 + (57 + 57 + 57) = 243
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As you can see, tknk's disc is unbalanced: ugml's stack is heavier than the other two. Even though the nodes above ugml are balanced, ugml itself is too heavy: it needs to be 8 units lighter for its stack to weigh 243 and keep the towers balanced. If this change were made, its weight would be 60.

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Given that exactly one program is the wrong weight, what would its weight need to be to balance the entire tower?

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Your puzzle answer was 910.

Both parts of this puzzle are complete! They provide two gold stars: **

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At this point, you should return to your advent calendar and try another puzzle.

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If you still want to see it, you can get your puzzle input.

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You can also this puzzle.

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+ + + + + + \ No newline at end of file diff --git a/problems/day08.html b/problems/day08.html new file mode 100644 index 0000000..b3eed51 --- /dev/null +++ b/problems/day08.html @@ -0,0 +1,149 @@ + + + + +Day 8 - Advent of Code 2017 + + + + + + + +

Advent of Code

Neil Smith (AoC++) 18*

      /*2017*/

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--- Day 8: I Heard You Like Registers ---

You receive a signal directly from the CPU. Because of your recent assistance with jump instructions, it would like you to compute the result of a series of unusual register instructions.

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Each instruction consists of several parts: the register to modify, whether to increase or decrease that register's value, the amount by which to increase or decrease it, and a condition. If the condition fails, skip the instruction without modifying the register. The registers all start at 0. The instructions look like this:

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b inc 5 if a > 1
+a inc 1 if b < 5
+c dec -10 if a >= 1
+c inc -20 if c == 10
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These instructions would be processed as follows:

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  • Because a starts at 0, it is not greater than 1, and so b is not modified.
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  • a is increased by 1 (to 1) because b is less than 5 (it is 0).
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  • c is decreased by -10 (to 10) because a is now greater than or equal to 1 (it is 1).
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  • c is increased by -20 (to -10) because c is equal to 10.
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After this process, the largest value in any register is 1.

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You might also encounter <= (less than or equal to) or != (not equal to). However, the CPU doesn't have the bandwidth to tell you what all the registers are named, and leaves that to you to determine.

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What is the largest value in any register after completing the instructions in your puzzle input?

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Your puzzle answer was 4647.

--- Part Two ---

To be safe, the CPU also needs to know the highest value held in any register during this process so that it can decide how much memory to allocate to these operations. For example, in the above instructions, the highest value ever held was 10 (in register c after the third instruction was evaluated).

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Your puzzle answer was 5590.

Both parts of this puzzle are complete! They provide two gold stars: **

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At this point, you should return to your advent calendar and try another puzzle.

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If you still want to see it, you can get your puzzle input.

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You can also this puzzle.

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+ + + + + + \ No newline at end of file diff --git a/problems/day09.html b/problems/day09.html new file mode 100644 index 0000000..5557429 --- /dev/null +++ b/problems/day09.html @@ -0,0 +1,181 @@ + + + + +Day 9 - Advent of Code 2017 + + + + + + + +

Advent of Code

Neil Smith (AoC++) 18*

      /*2017*/

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--- Day 9: Stream Processing ---

A large stream blocks your path. According to the locals, it's not safe to cross the stream at the moment because it's full of garbage. You look down at the stream; rather than water, you discover that it's a stream of characters.

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You sit for a while and record part of the stream (your puzzle input). The characters represent groups - sequences that begin with { and end with }. Within a group, there are zero or more other things, separated by commas: either another group or garbage. Since groups can contain other groups, a } only closes the most-recently-opened unclosed group - that is, they are nestable. Your puzzle input represents a single, large group which itself contains many smaller ones.

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Sometimes, instead of a group, you will find garbage. Garbage begins with < and ends with >. Between those angle brackets, almost any character can appear, including { and }. Within garbage, < has no special meaning.

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In a futile attempt to clean up the garbage, some program has canceled some of the characters within it using !: inside garbage, any character that comes after ! should be ignored, including <, >, and even another !.

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You don't see any characters that deviate from these rules. Outside garbage, you only find well-formed groups, and garbage always terminates according to the rules above.

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Here are some self-contained pieces of garbage:

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  • <>, empty garbage.
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  • <random characters>, garbage containing random characters.
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  • <<<<>, because the extra < are ignored.
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  • <{!>}>, because the first > is canceled.
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  • <!!>, because the second ! is canceled, allowing the > to terminate the garbage.
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  • <!!!>>, because the second ! and the first > are canceled.
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  • <{o"i!a,<{i<a>, which ends at the first >.
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Here are some examples of whole streams and the number of groups they contain:

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  • {}, 1 group.
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  • {{{}}}, 3 groups.
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  • {{},{}}, also 3 groups.
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  • {{{},{},{{}}}}, 6 groups.
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  • {<{},{},{{}}>}, 1 group (which itself contains garbage).
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  • {<a>,<a>,<a>,<a>}, 1 group.
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  • {{<a>},{<a>},{<a>},{<a>}}, 5 groups.
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  • {{<!>},{<!>},{<!>},{<a>}}, 2 groups (since all but the last > are canceled).
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Your goal is to find the total score for all groups in your input. Each group is assigned a score which is one more than the score of the group that immediately contains it. (The outermost group gets a score of 1.)

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  • {}, score of 1.
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  • {{{}}}, score of 1 + 2 + 3 = 6.
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  • {{},{}}, score of 1 + 2 + 2 = 5.
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  • {{{},{},{{}}}}, score of 1 + 2 + 3 + 3 + 3 + 4 = 16.
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  • {<a>,<a>,<a>,<a>}, score of 1.
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  • {{<ab>},{<ab>},{<ab>},{<ab>}}, score of 1 + 2 + 2 + 2 + 2 = 9.
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  • {{<!!>},{<!!>},{<!!>},{<!!>}}, score of 1 + 2 + 2 + 2 + 2 = 9.
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  • {{<a!>},{<a!>},{<a!>},{<ab>}}, score of 1 + 2 = 3.
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What is the total score for all groups in your input?

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Your puzzle answer was 11089.

--- Part Two ---

Now, you're ready to remove the garbage.

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To prove you've removed it, you need to count all of the characters within the garbage. The leading and trailing < and > don't count, nor do any canceled characters or the ! doing the canceling.

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  • <>, 0 characters.
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  • <random characters>, 17 characters.
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  • <<<<>, 3 characters.
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  • <{!>}>, 2 characters.
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  • <!!>, 0 characters.
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  • <!!!>>, 0 characters.
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  • <{o"i!a,<{i<a>, 10 characters.
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How many non-canceled characters are within the garbage in your puzzle input?

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Your puzzle answer was 5288.

Both parts of this puzzle are complete! They provide two gold stars: **

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At this point, you should return to your advent calendar and try another puzzle.

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If you still want to see it, you can get your puzzle input.

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You can also this puzzle.

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+ + + + + + \ No newline at end of file