76 lines
2.6 KiB
Markdown
76 lines
2.6 KiB
Markdown
## \-\-- Day 6: Probably a Fire Hazard \-\--
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Because your neighbors keep defeating you in the holiday house
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decorating contest year after year, you\'ve decided to deploy one
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million lights in a [1000x1000
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grid]{title="Hey, be glad I'm not asking for the resistance between two points!"}.
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Furthermore, because you\'ve been especially nice this year, Santa has
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mailed you instructions on how to display the ideal lighting
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configuration.
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Lights in your grid are numbered from 0 to 999 in each direction; the
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lights at each corner are at `0,0`, `0,999`, `999,999`, and `999,0`. The
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instructions include whether to `turn on`, `turn off`, or `toggle`
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various inclusive ranges given as coordinate pairs. Each coordinate pair
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represents opposite corners of a rectangle, inclusive; a coordinate pair
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like `0,0 through 2,2` therefore refers to 9 lights in a 3x3 square. The
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lights all start turned off.
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To defeat your neighbors this year, all you have to do is set up your
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lights by doing the instructions Santa sent you in order.
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For example:
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- `turn on 0,0 through 999,999` would turn on (or leave on) every
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light.
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- `toggle 0,0 through 999,0` would toggle the first line of 1000
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lights, turning off the ones that were on, and turning on the ones
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that were off.
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- `turn off 499,499 through 500,500` would turn off (or leave off) the
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middle four lights.
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After following the instructions, *how many lights are lit*?
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Your puzzle answer was `377891`.
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## \-\-- Part Two \-\-- {#part2}
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You just finish implementing your winning light pattern when you realize
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you mistranslated Santa\'s message from Ancient Nordic Elvish.
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The light grid you bought actually has individual brightness controls;
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each light can have a brightness of zero or more. The lights all start
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at zero.
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The phrase `turn on` actually means that you should increase the
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brightness of those lights by `1`.
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The phrase `turn off` actually means that you should decrease the
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brightness of those lights by `1`, to a minimum of zero.
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The phrase `toggle` actually means that you should increase the
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brightness of those lights by `2`.
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What is the *total brightness* of all lights combined after following
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Santa\'s instructions?
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For example:
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- `turn on 0,0 through 0,0` would increase the total brightness by
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`1`.
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- `toggle 0,0 through 999,999` would increase the total brightness by
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`2000000`.
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Your puzzle answer was `14110788`.
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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](/2015) 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](6/input).
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