71 lines
2.5 KiB
Markdown
71 lines
2.5 KiB
Markdown
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## \-\-- Day 5: A Maze of Twisty Trampolines, All Alike \-\--
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An urgent
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interrupt arrives
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from the CPU: it\'s trapped in a maze of jump instructions, and it would
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like assistance from any programs with spare cycles to help find the
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exit.
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The message includes a list of the offsets for each jump. Jumps are
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relative: `-1` moves to the previous instruction, and `2` skips the next
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one. Start at the first instruction in the list. The goal is to follow
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the jumps until one leads *outside* the list.
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In addition, these instructions are a little strange; after each jump,
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the offset of that instruction increases by `1`. So, if you come across
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an offset of `3`, you would move three instructions forward, but change
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it to a `4` for the next time it is encountered.
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For example, consider the following list of jump offsets:
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0
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3
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0
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1
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-3
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Positive jumps (\"forward\") move downward; negative jumps move upward.
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For legibility in this example, these offset values will be written all
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on one line, with the current instruction marked in parentheses. The
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following steps would be taken before an exit is found:
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- `(0) 3 0 1 -3 ` - *before* we have taken any steps.
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- `(1) 3 0 1 -3 ` - jump with offset `0` (that is, don\'t jump at
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all). Fortunately, the instruction is then incremented to `1`.
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- ` 2 (3) 0 1 -3 ` - step forward because of the instruction we just
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modified. The first instruction is incremented again, now to `2`.
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- ` 2 4 0 1 (-3)` - jump all the way to the end; leave a `4`
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behind.
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- ` 2 (4) 0 1 -2 ` - go back to where we just were; increment `-3`
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to `-2`.
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- ` 2 5 0 1 -2 ` - jump `4` steps forward, escaping the maze.
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In this example, the exit is reached in `5` steps.
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*How many steps* does it take to reach the exit?
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Your puzzle answer was `381680`.
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## \-\-- Part Two \-\-- {#part2}
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Now, the jumps are even stranger: after each jump, if the offset was
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*three or more*, instead *decrease* it by `1`. Otherwise, increase it by
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`1` as before.
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Using this rule with the above example, the process now takes `10`
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steps, and the offset values after finding the exit are left as
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`2 3 2 3 -1`.
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*How many steps* does it now take to reach the exit?
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Your puzzle answer was `29717847`.
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Both parts of this puzzle are complete! They provide two gold stars:
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\*\*
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At this point, you should [return to your Advent calendar](/2017) and
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try another puzzle.
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If you still want to see it, you can [get your puzzle
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input](5/input).
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