AoC 2017 Day 13: Firewall Puncher

Source: Packet Scanners

Part 1: Multiple layers are defined with rules of the form:

  • {index}: {depth}

Each layer will start at position 0, then once per tick will advance towards depth. Once it hits depth-1, it will return to position 0, taking 2*depth-1 per full cycle.

Calculate the sum of index * depth for any scanners that are at position 0 when you pass through them given an initial starting time.

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AoC 2017 Day 10: Knot Cool

Source: Knot Hash

Part 1: Starting with a list of the numbers from 1 to n and a list of lengths (as input):

  1. Initialize current_position and skip_size to 0
  2. For each length element in the lengths list:
  3. Reverse the first length elements of the list (starting at current_position)
  4. Move forward by length plus skip_size
  5. Increment skip_size by 1

After applying the above algorithm, what is the product of the first two elements in the list (from the original first position, not the current_position)?

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AoC 2017 Day 9: Garbage Gobbler

Source: Stream Processing

Part 1: An input stream can contain:

  • groups are delimited by { and }, groups are nestable and may contain garbage or data (objects within a group are comma delimited)
  • garbage is delimited by < and >, groups cannot be nested within garbage, a ! within garbage is an escape character: !> does not end a garbage segment

The score of a single group is equal to how many times it is nested (the innermost group of {{{}}} has score 3).

The score of a stream is the sum of the scores of all groups in that stream.

What is the total score of your input?

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AoC 2017 Day 7: Tree

Source: Recursive Circus

Part 1: A tree is defined as such:

  • node (weight) -> child1, child2, ...
  • node (weight)

Where a node always has a weight, but may or may not have child nodes.

What is the name of the root node of the tree (the node without a parent)?

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