Solution to problem 6 in Python

src/Year_2023/Day05.py

@@ -0,0 +1,258 @@
+# --- Day 5: If You Give A Seed A Fertilizer ---
+
+# You take the boat and find the gardener right where you were told he would be:
+# managing a giant "garden" that looks more to you like a farm.
+
+# "A water source? Island Island is the water source!" You point out that Snow
+# Island isn't receiving any water.
+
+# "Oh, we had to stop the water because we ran out of sand to filter it with!
+# Can't make snow with dirty water. Don't worry, I'm sure we'll get more sand
+# soon; we only turned off the water a few days... weeks... oh no." His face
+# sinks into a look of horrified realization.
+
+# "I've been so busy making sure everyone here has food that I completely forgot
+# to check why we stopped getting more sand! There's a ferry leaving soon that
+# is headed over in that direction - it's much faster than your boat. Could you
+# please go check it out?"
+
+# You barely have time to agree to this request when he brings up another.
+# "While you wait for the ferry, maybe you can help us with our food production
+# problem. The latest Island Island Almanac just arrived and we're having
+# trouble making sense of it."
+
+# The almanac (your puzzle input) lists all of the seeds that need to be
+# planted. It also lists what type of soil to use with each kind of seed, what
+# type of fertilizer to use with each kind of soil, what type of water to use
+# with each kind of fertilizer, and so on. Every type of seed, soil, fertilizer
+# and so on is identified with a number, but numbers are reused by each category
+# - that is, soil 123 and fertilizer 123 aren't necessarily related to each
+# other.
+
+# For example:
+
+# seeds: 79 14 55 13
+
+# seed-to-soil map:
+# 50 98 2
+# 52 50 48
+
+# soil-to-fertilizer map:
+# 0 15 37
+# 37 52 2
+# 39 0 15
+
+# fertilizer-to-water map:
+# 49 53 8
+# 0 11 42
+# 42 0 7
+# 57 7 4
+
+# water-to-light map:
+# 88 18 7
+# 18 25 70
+
+# light-to-temperature map:
+# 45 77 23
+# 81 45 19
+# 68 64 13
+
+# temperature-to-humidity map:
+# 0 69 1
+# 1 0 69
+
+# humidity-to-location map:
+# 60 56 37
+# 56 93 4
+
+# The almanac starts by listing which seeds need to be planted: seeds 79, 14,
+# 55, and 13.
+
+# The rest of the almanac contains a list of maps which describe how to convert
+# numbers from a source category into numbers in a destination category. That
+# is, the section that starts with seed-to-soil map: describes how to convert a
+# seed number (the source) to a soil number (the destination). This lets the
+# gardener and his team know which soil to use with which seeds, which water to
+# use with which fertilizer, and so on.
+
+# Rather than list every source number and its corresponding destination number
+# one by one, the maps describe entire ranges of numbers that can be converted.
+# Each line within a map contains three numbers: the destination range start,
+# the source range start, and the range length.
+
+# Consider again the example seed-to-soil map:
+
+# 50 98 2
+# 52 50 48
+
+# The first line has a destination range start of 50, a source range start of
+# 98, and a range length of 2. This line means that the source range starts at
+# 98 and contains two values: 98 and 99. The destination range is the same
+# length, but it starts at 50, so its two values are 50 and 51. With this
+# information, you know that seed number 98 corresponds to soil number 50 and
+# that seed number 99 corresponds to soil number 51.
+
+# The second line means that the source range starts at 50 and contains 48
+# values: 50, 51, ..., 96, 97. This corresponds to a destination range starting
+# at 52 and also containing 48 values: 52, 53, ..., 98, 99. So, seed number 53
+# corresponds to soil number 55.
+
+# Any source numbers that aren't mapped correspond to the same destination
+# number. So, seed number 10 corresponds to soil number 10.
+
+# So, the entire list of seed numbers and their corresponding soil numbers looks
+# like this:
+
+# seed  soil
+# 0     0
+# 1     1
+# ...   ...
+# 48    48
+# 49    49
+# 50    52
+# 51    53
+# ...   ...
+# 96    98
+# 97    99
+# 98    50
+# 99    51
+
+# With this map, you can look up the soil number required for each initial seed
+# number:
+
+#     Seed number 79 corresponds to soil number 81.
+#     Seed number 14 corresponds to soil number 14.
+#     Seed number 55 corresponds to soil number 57.
+#     Seed number 13 corresponds to soil number 13.
+
+# The gardener and his team want to get started as soon as possible, so they'd
+# like to know the closest location that needs a seed. Using these maps, find
+# the lowest location number that corresponds to any of the initial seeds. To do
+# this, you'll need to convert each seed number through other categories until
+# you can find its corresponding location number. In this example, the
+# corresponding types are:
+
+#     Seed 79, soil 81, fertilizer 81, water 81, light 74, temperature 78,
+# humidity 78, location 82.
+#     Seed 14, soil 14, fertilizer 53, water 49, light 42, temperature 42,
+# humidity 43, location 43.
+#     Seed 55, soil 57, fertilizer 57, water 53, light 46, temperature 82,
+# humidity 82, location 86.
+#     Seed 13, soil 13, fertilizer 52, water 41, light 34, temperature 34,
+# humidity 35, location 35.
+
+# So, the lowest location number in this example is 35.
+
+# What is the lowest location number that corresponds to any of the initial seed
+# numbers?
+
+with open("files/P5.txt") as f:
+    almanac = [line for line in f.read().strip().split("\n\n")]
+
+seed, *maps = almanac
+seeds = [int(s) for s in seed.split(":")[1].split()]
+mappings = [
+    [[int(i) for i in line.split()] for line in m.splitlines()[1:]]
+    for m in maps
+]
+
+
+def part1():
+    locations = seeds
+    for mapping in mappings:
+        new_locations = []
+        for location in locations:
+            new_val = location
+            for destination, start, size in mapping:
+                if start <= location < start + size:
+                    new_val = location - start + destination
+                    break
+            new_locations.append(new_val)
+        locations = new_locations
+
+    print(f"The lowest location is {min(locations)}")
+
+
+# --- Part Two ---
+
+# Everyone will starve if you only plant such a small number of seeds.
+# Re-reading the almanac, it looks like the seeds: line actually describes
+# ranges of seed numbers.
+
+# The values on the initial seeds: line come in pairs. Within each pair, the
+# first value is the start of the range and the second value is the length of
+# the range. So, in the first line of the example above:
+
+# seeds: 79 14 55 13
+
+# This line describes two ranges of seed numbers to be planted in the garden.
+# The first range starts with seed number 79 and contains 14 values: 79, 80,
+# ..., 91, 92. The second range starts with seed number 55 and contains 13
+# values: 55, 56, ..., 66, 67.
+
+# Now, rather than considering four seed numbers, you need to consider a total
+# of 27 seed numbers.
+
+# In the above example, the lowest location number can be obtained from seed
+# number 82, which corresponds to soil 84, fertilizer 84, water 84, light 77,
+# temperature 45, humidity 46, and location 46. So, the lowest location number
+# is 46.
+
+# Consider all of the initial seed numbers listed in the ranges on the first
+# line of the almanac. What is the lowest location number that corresponds to
+# any of the initial seed numbers?
+
+
+def get_ranges(span_start, span_end, map_start, map_end):
+    if span_start < map_start and map_end < span_end:
+        return [(map_start, map_end)], [
+            (span_start, map_start - 1),
+            (map_end + 1, span_end),
+        ]
+    elif map_start <= span_start and span_end <= map_end:
+        return [(span_start, span_end)], []
+    elif span_start < map_start <= span_end:
+        return [(map_start, span_end)], [(span_start, map_start - 1)]
+    elif span_start <= map_end < span_end:
+        return [(span_start, map_end)], [(map_end + 1, span_end)]
+    else:
+        return [], [(span_start, span_end)]
+
+
+new_mappings = [
+    [
+        [destination - start, start, start + size - 1]
+        for destination, start, size in m
+    ]
+    for m in mappings
+]
+
+
+def part2():
+    ranges = [
+        (seeds[i], seeds[i] + seeds[i + 1] - 1)
+        for i in range(0, len(seeds), 2)
+    ]
+
+    for mapping in new_mappings:
+        new_ranges = []
+        for seed_span in ranges:
+            unprocessed = [seed_span]
+            for offset, map_start, map_end in mapping:
+                new_unprocessed = []
+                for span_start, span_end in unprocessed:
+                    map1, map2 = get_ranges(
+                        span_start, span_end, map_start, map_end
+                    )
+                    new_unprocessed += map2
+                    new_ranges += [(a + offset, b + offset) for a, b in map1]
+                unprocessed = new_unprocessed
+            new_ranges += unprocessed
+        ranges = new_ranges
+
+    print(f"The lowest location is {min(idx for idx, _ in ranges)}")
+
+
+if __name__ == "__main__":
+    part1()
+    part2()

src/Year_2023/Day06.py

@@ -0,0 +1,152 @@
+# --- Day 6: Wait For It ---
+
+# The ferry quickly brings you across Island Island. After asking around, you
+# discover that there is indeed normally a large pile of sand somewhere near
+# here, but you don't see anything besides lots of water and the small island
+# where the ferry has docked.
+
+# As you try to figure out what to do next, you notice a poster on a wall near
+# the ferry dock. "Boat races! Open to the public! Grand prize is an
+# all-expenses-paid trip to Desert Island!" That must be where the sand comes
+# from! Best of all, the boat races are starting in just a few minutes.
+
+# You manage to sign up as a competitor in the boat races just in time. The
+# organizer explains that it's not really a traditional race - instead, you will
+# get a fixed amount of time during which your boat has to travel as far as it
+# can, and you win if your boat goes the farthest.
+
+# As part of signing up, you get a sheet of paper (your puzzle input) that lists
+# the time allowed for each race and also the best distance ever recorded in
+# that race. To guarantee you win the grand prize, you need to make sure you go
+# farther in each race than the current record holder.
+
+# The organizer brings you over to the area where the boat races are held. The
+# boats are much smaller than you expected - they're actually toy boats, each
+# with a big button on top. Holding down the button charges the boat, and
+# releasing the button allows the boat to move. Boats move faster if their
+# button was held longer, but time spent holding the button counts against the
+# total race time. You can only hold the button at the start of the race, and
+# boats don't move until the button is released.
+
+# For example:
+
+# Time:      7  15   30
+# Distance:  9  40  200
+
+# This document describes three races:
+
+#     The first race lasts 7 milliseconds. The record distance in this race is
+# 9 millimeters.
+#     The second race lasts 15 milliseconds. The record distance in this race is
+# 40 millimeters.
+#     The third race lasts 30 milliseconds. The record distance in this race is
+# 200 millimeters.
+
+# Your toy boat has a starting speed of zero millimeters per millisecond. For
+# each whole millisecond you spend at the beginning of the race holding down the
+# button, the boat's speed increases by one millimeter per millisecond.
+
+# So, because the first race lasts 7 milliseconds, you only have a few options:
+
+#     Don't hold the button at all (that is, hold it for 0 milliseconds) at the
+# start of the race. The boat won't move; it will have traveled 0 millimeters by
+# the end of the race.
+#     Hold the button for 1 millisecond at the start of the race. Then, the boat
+# will travel at a speed of 1 millimeter per millisecond for 6 milliseconds,
+# reaching a total distance traveled of 6 millimeters.
+#     Hold the button for 2 milliseconds, giving the boat a speed of 2
+# millimeters per millisecond. It will then get 5 milliseconds to move, reaching
+# a total distance of 10 millimeters.
+#     Hold the button for 3 milliseconds. After its remaining 4 milliseconds of
+# travel time, the boat will have gone 12 millimeters.
+#     Hold the button for 4 milliseconds. After its remaining 3 milliseconds of
+# travel time, the boat will have gone 12 millimeters.
+#     Hold the button for 5 milliseconds, causing the boat to travel a total of
+# 10 millimeters.
+#     Hold the button for 6 milliseconds, causing the boat to travel a total of
+# 6 millimeters.
+#     Hold the button for 7 milliseconds. That's the entire duration of the
+# race. You never let go of the button. The boat can't move until you let go of
+# the button. Please make sure you let go of the button so the boat gets to
+# move. 0 millimeters.
+
+# Since the current record for this race is 9 millimeters, there are actually 4
+# different ways you could win: you could hold the button for 2, 3, 4, or 5
+# milliseconds at the start of the race.
+
+# In the second race, you could hold the button for at least 4 milliseconds and
+# at most 11 milliseconds and beat the record, a total of 8 different ways to
+# win.
+
+# In the third race, you could hold the button for at least 11 milliseconds and
+# no more than 19 milliseconds and still beat the record, a total of 9 ways you
+# could win.
+
+# To see how much margin of error you have, determine the number of ways you can
+# beat the record in each race; in this example, if you multiply these values
+# together, you get 288 (4 * 8 * 9).
+
+# Determine the number of ways you could beat the record in each race. What do
+# you get if you multiply these numbers together?
+
+with open("files/P6.txt") as f:
+    times, distances = [line for line in f.read().strip().split("\n")]
+
+times = [int(t) for t in times.split(":")[1].split()]
+distances = [int(d) for d in distances.split(":")[1].split()]
+
+
+def part1():
+    total = 1
+    for idx, time in enumerate(times):
+        res = 0
+        for t in range(time):
+            d = t * (time - t)
+            if d > distances[idx]:
+                res += 1
+        total *= res
+
+    print(f"There are {total} ways of beating the record")
+
+
+# --- Part Two ---
+
+# As the race is about to start, you realize the piece of paper with race times
+# and record distances you got earlier actually just has very bad kerning.
+# There's really only one race - ignore the spaces between the numbers on each
+# line.
+
+# So, the example from before:
+
+# Time:      7  15   30
+# Distance:  9  40  200
+
+# ...now instead means this:
+
+# Time:      71530
+# Distance:  940200
+
+# Now, you have to figure out how many ways there are to win this single race.
+# In this example, the race lasts for 71530 milliseconds and the record distance
+# you need to beat is 940200 millimeters. You could hold the button anywhere
+# from 14 to 71516 milliseconds and beat the record, a total of 71503 ways!
+
+# How many ways can you beat the record in this one much longer race?
+
+time = int("".join(str(t) for t in times))
+distance = int("".join(str(d) for d in distances))
+
+
+def part2():
+    total = 0
+    for t in range(time):
+        d = t * (time - t)
+        if d > distance:
+            total += 1
+
+    print(f"There are {total} ways of beating the record")
+
+
+if __name__ == "__main__":
+    part1()
+    part2()

src/Year_2023/files/P5.txt

@@ -0,0 +1,237 @@
+seeds: 4188359137 37519573 3736161691 172346126 2590035450 66446591 209124047 106578880 1404892542 30069991 3014689843 117426545 2169439765 226325492 1511958436 177344330 1822605035 51025110 382778843 823998526
+
+seed-to-soil map:
+1014943420 3864598346 36796924
+3481858860 1134944893 176050938
+1463359964 377309295 172917932
+1909673912 2511534001 114785858
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+
+soil-to-fertilizer map:
+3211509025 2411974869 518394
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+
+fertilizer-to-water map:
+3919934952 4034286493 116558226
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+
+water-to-light map:
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+
+light-to-temperature map:
+3239555722 2588818955 376881377
+413170934 1615450109 438931580
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+
+temperature-to-humidity map:
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+
+humidity-to-location map:
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src/Year_2023/files/P6.txt

@@ -0,0 +1,2 @@
+Time:        61     70     90     66
+Distance:   643   1184   1362   1041