day 7

code/aoc2021-programs.cabal

@@ -38,3 +38,24 @@ executable aoc2021-04
    hs-source-dirs: src/04
    build-depends: base
    default-language: Haskell2010
+
+executable aoc2021-05
+   main-is: Main.hs
+   ghc-options: -O2 -Wall
+   hs-source-dirs: src/05
+   build-depends: base, parsec
+   default-language: Haskell2010
+
+executable aoc2021-06
+   main-is: Main.hs
+   ghc-options: -O2 -Wall
+   hs-source-dirs: src/06
+   build-depends: base
+   default-language: Haskell2010
+
+executable aoc2021-07
+   main-is: Main.hs
+   ghc-options: -O2 -Wall
+   hs-source-dirs: src/07
+   build-depends: base
+   default-language: Haskell2010

code/src/05/05-description.txt

@@ -0,0 +1,71 @@
+--- Day 5: Hydrothermal Venture ---
+You come across a field of hydrothermal vents on the ocean floor! These vents constantly produce large, opaque clouds, so it would be best to avoid them if possible.
+
+They tend to form in lines; the submarine helpfully produces a list of nearby lines of vents (your puzzle input) for you to review. For example:
+
+0,9 -> 5,9
+8,0 -> 0,8
+9,4 -> 3,4
+2,2 -> 2,1
+7,0 -> 7,4
+6,4 -> 2,0
+0,9 -> 2,9
+3,4 -> 1,4
+0,0 -> 8,8
+5,5 -> 8,2
+Each line of vents is given as a line segment in the format x1,y1 -> x2,y2 where x1,y1 are the coordinates of one end the line segment and x2,y2 are the coordinates of the other end. These line segments include the points at both ends. In other words:
+
+An entry like 1,1 -> 1,3 covers points 1,1, 1,2, and 1,3.
+An entry like 9,7 -> 7,7 covers points 9,7, 8,7, and 7,7.
+For now, only consider horizontal and vertical lines: lines where either x1 = x2 or y1 = y2.
+
+So, the horizontal and vertical lines from the above list would produce the following diagram:
+
+.......1..
+..1....1..
+..1....1..
+.......1..
+.112111211
+..........
+..........
+..........
+..........
+222111....
+In this diagram, the top left corner is 0,0 and the bottom right corner is 9,9. Each position is shown as the number of lines which cover that point or . if no line covers that point. The top-left pair of 1s, for example, comes from 2,2 -> 2,1; the very bottom row is formed by the overlapping lines 0,9 -> 5,9 and 0,9 -> 2,9.
+
+To avoid the most dangerous areas, you need to determine the number of points where at least two lines overlap. In the above example, this is anywhere in the diagram with a 2 or larger - a total of 5 points.
+
+Consider only horizontal and vertical lines. At how many points do at least two lines overlap?
+
+Your puzzle answer was 5690.
+
+--- Part Two ---
+Unfortunately, considering only horizontal and vertical lines doesn't give you the full picture; you need to also consider diagonal lines.
+
+Because of the limits of the hydrothermal vent mapping system, the lines in your list will only ever be horizontal, vertical, or a diagonal line at exactly 45 degrees. In other words:
+
+An entry like 1,1 -> 3,3 covers points 1,1, 2,2, and 3,3.
+An entry like 9,7 -> 7,9 covers points 9,7, 8,8, and 7,9.
+Considering all lines from the above example would now produce the following diagram:
+
+1.1....11.
+.111...2..
+..2.1.111.
+...1.2.2..
+.112313211
+...1.2....
+..1...1...
+.1.....1..
+1.......1.
+222111....
+You still need to determine the number of points where at least two lines overlap. In the above example, this is still anywhere in the diagram with a 2 or larger - now a total of 12 points.
+
+Consider all of the lines. At how many points do at least two lines overlap?
+
+Your puzzle answer was 17741.
+
+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.

code/src/05/n.txt

@@ -1,4 +0,0 @@
-1,9 -> 9,9
-9,1 -> 1,1
-1,1 -> 1,9
-1,1 -> 1,9

code/src/05/test.txt

@@ -1,10 +0,0 @@
-0,9 -> 5,9
-8,0 -> 0,8
-9,4 -> 3,4
-2,2 -> 2,1
-7,0 -> 7,4
-6,4 -> 2,0
-0,9 -> 2,9
-3,4 -> 1,4
-0,0 -> 8,8
-5,5 -> 8,2

code/src/07/07-description.txt

@@ -0,0 +1,64 @@
+--- Day 7: The Treachery of Whales ---
+A giant whale has decided your submarine is its next meal, and it's much faster than you are. There's nowhere to run!
+
+Suddenly, a swarm of crabs (each in its own tiny submarine - it's too deep for them otherwise) zooms in to rescue you! They seem to be preparing to blast a hole in the ocean floor; sensors indicate a massive underground cave system just beyond where they're aiming!
+
+The crab submarines all need to be aligned before they'll have enough power to blast a large enough hole for your submarine to get through. However, it doesn't look like they'll be aligned before the whale catches you! Maybe you can help?
+
+There's one major catch - crab submarines can only move horizontally.
+
+You quickly make a list of the horizontal position of each crab (your puzzle input). Crab submarines have limited fuel, so you need to find a way to make all of their horizontal positions match while requiring them to spend as little fuel as possible.
+
+For example, consider the following horizontal positions:
+
+16,1,2,0,4,2,7,1,2,14
+This means there's a crab with horizontal position 16, a crab with horizontal position 1, and so on.
+
+Each change of 1 step in horizontal position of a single crab costs 1 fuel. You could choose any horizontal position to align them all on, but the one that costs the least fuel is horizontal position 2:
+
+Move from 16 to 2: 14 fuel
+Move from 1 to 2: 1 fuel
+Move from 2 to 2: 0 fuel
+Move from 0 to 2: 2 fuel
+Move from 4 to 2: 2 fuel
+Move from 2 to 2: 0 fuel
+Move from 7 to 2: 5 fuel
+Move from 1 to 2: 1 fuel
+Move from 2 to 2: 0 fuel
+Move from 14 to 2: 12 fuel
+This costs a total of 37 fuel. This is the cheapest possible outcome; more expensive outcomes include aligning at position 1 (41 fuel), position 3 (39 fuel), or position 10 (71 fuel).
+
+Determine the horizontal position that the crabs can align to using the least fuel possible. How much fuel must they spend to align to that position?
+
+Your puzzle answer was 344735.
+
+--- Part Two ---
+The crabs don't seem interested in your proposed solution. Perhaps you misunderstand crab engineering?
+
+As it turns out, crab submarine engines don't burn fuel at a constant rate. Instead, each change of 1 step in horizontal position costs 1 more unit of fuel than the last: the first step costs 1, the second step costs 2, the third step costs 3, and so on.
+
+As each crab moves, moving further becomes more expensive. This changes the best horizontal position to align them all on; in the example above, this becomes 5:
+
+Move from 16 to 5: 66 fuel
+Move from 1 to 5: 10 fuel
+Move from 2 to 5: 6 fuel
+Move from 0 to 5: 15 fuel
+Move from 4 to 5: 1 fuel
+Move from 2 to 5: 6 fuel
+Move from 7 to 5: 3 fuel
+Move from 1 to 5: 10 fuel
+Move from 2 to 5: 6 fuel
+Move from 14 to 5: 45 fuel
+This costs a total of 168 fuel. This is the new cheapest possible outcome; the old alignment position (2) now costs 206 fuel instead.
+
+Determine the horizontal position that the crabs can align to using the least fuel possible so they can make you an escape route! How much fuel must they spend to align to that position?
+
+Your puzzle answer was 96798233.
+
+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.

code/src/07/07-input.txt

@@ -0,0 +1 @@
+1101,1,29,67,1102,0,1,65,1008,65,35,66,1005,66,28,1,67,65,20,4,0,1001,65,1,65,1106,0,8,99,35,67,101,99,105,32,110,39,101,115,116,32,112,97,115,32,117,110,101,32,105,110,116,99,111,100,101,32,112,114,111,103,114,97,109,10,82,1266,26,290,428,9,676,880,16,340,1578,839,23,32,721,88,837,118,543,198,836,870,105,44,214,184,52,330,213,1224,1211,481,1707,409,78,1096,995,420,808,50,65,635,1186,228,5,359,290,1241,757,323,11,447,522,8,170,265,632,321,9,1707,1005,1194,466,137,982,905,373,158,601,247,373,202,432,168,694,785,568,144,576,1006,143,1506,298,1790,146,182,535,895,42,296,278,469,118,292,1375,206,235,1545,63,81,49,1405,660,41,1009,226,133,324,1250,113,10,687,223,78,10,745,21,55,1041,149,519,57,589,123,901,416,200,112,35,6,873,353,539,665,75,207,80,787,322,1026,178,19,630,12,263,1136,71,220,143,688,101,88,1600,16,141,55,64,436,19,889,267,470,884,31,546,846,601,15,84,399,83,1054,4,1417,766,525,162,640,73,2,110,189,494,85,44,263,618,583,263,591,1139,21,1593,187,115,520,142,887,3,12,565,78,88,114,803,157,307,1007,1365,1063,1481,431,410,125,19,1123,3,433,73,273,25,438,314,111,369,1188,526,516,509,1,186,143,1335,689,436,1002,260,791,12,36,380,80,306,173,45,24,856,1892,255,11,12,1221,422,8,1214,327,851,85,375,115,325,213,725,720,669,465,577,1,28,331,123,297,267,1586,478,259,572,204,365,461,618,364,5,630,377,26,259,331,956,164,89,115,1328,823,48,625,922,236,577,1113,251,156,846,261,500,73,1607,281,267,64,2,392,115,682,1833,861,1093,1165,52,1643,59,180,787,298,274,304,381,196,511,352,793,1043,984,30,85,190,109,276,303,251,1601,939,726,5,213,915,235,780,43,1212,1466,353,364,507,129,1109,1307,113,109,342,756,898,1015,63,949,127,887,175,91,409,1069,88,600,101,434,1021,477,1073,22,549,145,712,730,160,7,123,27,566,689,172,1496,543,154,345,442,3,860,47,69,319,487,17,1086,1305,329,788,738,688,421,139,1629,499,824,276,13,1033,885,522,140,328,113,311,297,252,33,168,1059,94,469,1816,2,107,149,652,350,200,173,367,100,229,219,400,43,283,1551,752,278,99,648,190,190,337,44,191,462,454,544,261,142,1204,231,924,209,858,768,211,223,186,1452,687,320,343,444,94,1231,285,324,431,36,309,705,672,69,1082,83,269,515,369,117,951,489,117,249,47,350,1408,93,203,800,1151,526,785,721,240,74,605,501,533,512,337,12,720,787,1521,894,112,187,170,1020,339,77,565,691,1141,129,1020,60,505,1383,178,1262,1302,750,743,1108,43,634,135,738,810,628,1807,938,530,61,1384,42,79,276,336,1434,1286,393,145,9,94,945,113,76,88,856,78,1750,499,994,527,1102,266,1164,796,143,726,480,357,577,910,460,448,379,402,1576,1353,257,1044,651,1206,44,126,353,1099,934,892,379,710,988,1041,367,116,377,546,1222,830,259,10,6,385,856,343,793,490,165,367,1022,1065,95,135,426,184,270,227,456,673,90,1363,1127,387,93,138,202,184,1071,134,15,813,134,200,80,144,128,1502,574,868,487,118,42,48,1135,1107,57,418,1093,1508,229,26,154,652,94,1254,171,502,407,276,1098,18,1000,345,150,123,211,1517,1005,590,1413,63,80,510,502,76,476,47,405,186,143,344,286,1277,934,64,512,12,1026,264,68,1420,10,245,10,352,6,585,567,48,428,816,1525,180,346,350,34,100,42,1354,699,265,445,1719,425,8,604,129,111,71,110,1170,703,36,317,198,104,655,95,1046,327,161,853,400,224,797,1221,794,684,321,1279,1,95,1253,671,203,43,220,55,90,1606,359,52,775,76,422,403,305,614,196,244,102,519,122,451,1610,79,709,336,1374,735,478,1123,658,906,615,688,561,518,39,1084,608,54,739,416,1648,1838,1280,1039,35,552,299,142,56,1217,1356,30,12,102,731,1343,224,452,304,1808,546,583,710,33,149,1126,565,314,745,22,115,263,813,113,52,308,944,981,441,544,129,1258,299,885,717,536,253,3,612,29,130,1099,1455,38,501,578,13,347,729,166,772,230,518,488,430,1093,140,16,120,1603,794,174,1361,1657,825,444,176,815,1353,469,264,191,988,12,104,11,1518,1096,347,606,350,18,1376,430,182,1229,131,111,731,174,111,304,715,35,410,701,78,46,390,291,1008,1779,620,2,1378,199,331,334,708,446,1141,773,159,702,716,13,582,161,259,90,180,607,539,611,312,622,151,522,921,150,522,273,421,842,111,21,159,148

code/src/07/Main.hs

@@ -0,0 +1,34 @@
+module Main where
+
+import Data.List
+
+main :: IO ()
+main = do
+  raw <- getLine
+  let input = map read $ words $ repCom raw
+  putStrLn $ "day7a: " ++ (show $ solveA input)
+  putStrLn $ "day7b: " ++ (show $ solveB input)
+
+repCom :: String -> String
+repCom = map f
+  where f c = if c == ',' then ' ' else c
+
+solveA :: [Int] -> Int
+solveA is = minimum $ map f us
+  where
+    f x = sum $ map (absdiff x) is
+    us = nub is
+
+solveB :: [Int] -> Int
+solveB is = minimum $ map f [low .. high]
+  where
+    high = maximum us
+    low = minimum us
+    f x = sum $ map (expdiff x) is
+    us = nub is
+
+absdiff :: Int -> Int -> Int
+absdiff x y = abs (x - y)
+
+expdiff :: Int -> Int -> Int
+expdiff x y = sum $ take (absdiff x y) [1..]