2024 begins! day 1

Author: lucianoq

2024/1/Makefile

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+main1:
+	go build -o main1 main1.go
+
+main2:
+	go build -o main2 main2.go
+
+.PHONY: run1 run2 clean
+
+run1: main1
+	./main1 <input
+
+run2: main2
+	./main2 <input
+
+clean:
+	rm -f main1 main2

2024/1/assignment

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+--- Day 1: Historian Hysteria ---
+
+   The Chief Historian is always present for the big Christmas sleigh
+   launch, but nobody has seen him in months! Last anyone heard, he was
+   visiting locations that are historically significant to the North Pole;
+   a group of Senior Historians has asked you to accompany them as they
+   check the places they think he was most likely to visit.
+
+   As each location is checked, they will mark it on their list with a
+   star . They figure the Chief Historian must be in one of the first
+   fifty places they'll look, so in order to save Christmas, you need to
+   help them get fifty stars on their list before Santa takes off on
+   December 25th.
+
+   Collect stars by solving puzzles. Two puzzles will be made available on
+   each day in the Advent calendar; the second puzzle is unlocked when you
+   complete the first. Each puzzle grants one star . Good luck!
+
+   You haven't even left yet and the group of Elvish Senior Historians has
+   already hit a problem: their list of locations to check is currently
+   empty . Eventually, someone decides that the best place to check first
+   would be the Chief Historian's office.
+
+   Upon pouring into the office, everyone confirms that the Chief
+   Historian is indeed nowhere to be found. Instead, the Elves discover an
+   assortment of notes and lists of historically significant locations!
+   This seems to be the planning the Chief Historian was doing before he
+   left. Perhaps these notes can be used to determine which locations to
+   search?
+
+   Throughout the Chief's office, the historically significant locations
+   are listed not by name but by a unique number called the location ID .
+   To make sure they don't miss anything, The Historians split into two
+   groups, each searching the office and trying to create their own
+   complete list of location IDs.
+
+   There's just one problem: by holding the two lists up side by side
+   (your puzzle input), it quickly becomes clear that the lists aren't
+   very similar. Maybe you can help The Historians reconcile their lists?
+
+   For example:
+
+        3   4
+        4   3
+        2   5
+        1   3
+        3   9
+        3   3
+
+   Maybe the lists are only off by a small amount! To find out, pair up
+   the numbers and measure how far apart they are. Pair up the smallest
+   number in the left list with the smallest number in the right list ,
+   then the second-smallest left number with the second-smallest right
+   number , and so on.
+
+   Within each pair, figure out how far apart the two numbers are; you'll
+   need to add up all of those distances . For example, if you pair up a 3
+   from the left list with a 7 from the right list, the distance apart is
+   4 ; if you pair up a 9 with a 3 , the distance apart is 6 .
+
+   In the example list above, the pairs and distances would be as follows:
+     * The smallest number in the left list is 1 , and the smallest number
+       in the right list is 3 . The distance between them is 2 .
+     * The second-smallest number in the left list is 2 , and the
+       second-smallest number in the right list is another 3 . The
+       distance between them is 1 .
+     * The third-smallest number in both lists is 3 , so the distance
+       between them is 0 .
+     * The next numbers to pair up are 3 and 4 , a distance of 1 .
+     * The fifth-smallest numbers in each list are 3 and 5 , a distance of
+       2 .
+     * Finally, the largest number in the left list is 4 , while the
+       largest number in the right list is 9 ; these are a distance 5
+       apart.
+
+   To find the total distance between the left list and the right list,
+   add up the distances between all of the pairs you found. In the example
+   above, this is 2 + 1 + 0 + 1 + 2 + 5 , a total distance of 11 !
+
+   Your actual left and right lists contain many location IDs. What is the
+   total distance between your lists?
+
+--- Part Two ---
+
+   Your analysis only confirmed what everyone feared: the two lists of
+   location IDs are indeed very different.
+
+   Or are they?
+
+   The Historians can't agree on which group made the mistakes or how to
+   read most of the Chief's handwriting, but in the commotion you notice
+   an interesting detail: a lot of location IDs appear in both lists!
+   Maybe the other numbers aren't location IDs at all but rather
+   misinterpreted handwriting.
+
+   This time, you'll need to figure out exactly how often each number from
+   the left list appears in the right list. Calculate a total similarity
+   score by adding up each number in the left list after multiplying it by
+   the number of times that number appears in the right list.
+
+   Here are the same example lists again:
+
+        3   4
+        4   3
+        2   5
+        1   3
+        3   9
+        3   3
+
+   For these example lists, here is the process of finding the similarity
+   score:
+     * The first number in the left list is 3 . It appears in the right
+       list three times, so the similarity score increases by 3 * 3 = 9 .
+     * The second number in the left list is 4 . It appears in the right
+       list once, so the similarity score increases by 4 * 1 = 4 .
+     * The third number in the left list is 2 . It does not appear in the
+       right list, so the similarity score does not increase ( 2 * 0 = 0
+       ).
+     * The fourth number, 1 , also does not appear in the right list.
+     * The fifth number, 3 , appears in the right list three times; the
+       similarity score increases by 9 .
+     * The last number, 3 , appears in the right list three times; the
+       similarity score again increases by 9 .
+
+   So, for these example lists, the similarity score at the end of this
+   process is 31 ( 9 + 4 + 0 + 0 + 9 + 9 ).
+
+   Once again consider your left and right lists. What is their similarity
+   score?