Advent of Code 2021: Python Solution

Advent of Code 2021: Python Solutions

I am not good at solving problems fast but I try to do them with best I could. And here in this blog post, I try to show my solutions of all days in one post. For the Jupyter Notebook, please refer to this repository. The code will be updated once solved but I am preparing headers, code blocks and links before day starts. Also I am not trying to get into any rank.

Before Solving Day 1

Last year I had hard time reading input data and thus, this year I am using some helper functions. First of them is get_data().

def get_data(day=1):
    """
    Returns test and real data in list format.
    Raw data should be maintained as:
        [test data]
        Split From Here
        [actual data]
    """
    file_name = f"data/day{day}.txt"

    with open(file_name) as fp:
        data = fp.read().strip().split("Split From Here")
        data = [d.strip().split("\n") for d in data]
        return data
get_data()

I created a folder data in working directory and inside there will be a text files with names as day[current_day].txt. The file will contain the test input in first half and real input in second half. The separator will be a string "Split From Here".

Additionally, to make things faster, I created text files for all days with below code:

for i in range(2, 26):
    with open(f"data/day{i}.txt","w") as fp:
        fp.writelines("Split From Here")

Day 1

Here is the problem link.

Get Data

data,data1 = get_data() 
data = list(map(int, data))
data1 = list(map(int, data1))

data

Part 1

pd = None
res = []
for d in data:
    if pd is None:
        res.append(None)
    else:
        if pd>d:
            res.append("0")
        else:
            res.append("1")
    pd=d
res.count("1")

The result will be printed out and it is 7 for test data. Changing variable data1 from data in above code will give the answer.

Part 2

w = []
wsum = []
i = 0
ps = None
for j in range(3, len(data1)+1):
    wsum.append(sum(data1[i:j]))
    i+=1

pd = None
res1 = []
for d in wsum:
    if pd is None:
        res1.append(None)
    else:
        if pd>=d:
            res1.append("0")
        else:
            res1.append("1")
    pd=d
res1.count("1")

Day 2

Here is the problem link.

Part 1

data,data1 = get_data(day=2)

hs = 0
vs = 0

for d in data:
    k,v = d.split()

    if k =="forward":
        hs+=int(v)
    elif k == "down":
        vs+=int(v)
    elif k=="up":
        vs-=int(v)

print(hs*vs)

The test output will be 150 and for real output, should change the variable to data1.

Part 2

hs = 0
vs = 0
aim = 0

for d in data1:
    k,v = d.split()
    v = int(v)

    if k =="forward":
        hs+=v
        vs+=aim*v
    elif k == "down":
        aim+=v
#         vs+=v
    elif k=="up":
        aim-=v
#         vs-=v

print(hs*vs)

Day 3

Here is the problem link.

Part 1

from collections import Counter
import numpy as np

data,data1 = get_data(day=3)

def part1(inp):
    cs = len(inp[0])
    dt = [int(d) for dt in inp for d in dt]
    dt = np.array(dt).reshape(-1, cs)

    print(dt[0])

    counts = [sorted(dict(Counter(dt[:, i])).items(), key=lambda item: item[1]) for i in range(len(dt[0]))]
    counts = np.array(counts).reshape(-1,2)

    minidx = np.arange(0, len(counts), 2)
    maxidx = np.arange(1, len(counts), 2)

    minv = int("".join(list(map(str, counts[minidx, 0]))), 2)
    maxv = int("".join(list(map(str, counts[maxidx, 0]))), 2)
    print(minv, maxv)
    print(minv*maxv)
part1(data)

The result of test input is:

[0 0 1 0 0]
9 22
198

All hail to the NumPy. For real input, should change the variable name data to data1 and call part1.

Part 2

def o2(dt):
    ndt = dt.copy()
    #print(len(ndt[0]))

    curr_c = 0
    while curr_c<len(dt[0]):
        print(f"Current Col: {curr_c}")
        counts = [sorted(dict(Counter(ndt[:, curr_c])).items(), key=lambda item: item[1])]
        counts = np.array(counts).reshape(-1,2)
        if len(counts)>1:
            if counts[0, 1]==counts[1, 1]:
                ndt = ndt[ndt[:,curr_c]==1]
            else:
                ndt = ndt[ndt[:,curr_c]==counts[1][0]]
        else:
            ndt = ndt[ndt[:,curr_c]==counts[1][0]]
        print(f"Current Col: {curr_c} Rows: {len(ndt)}")
#         print(counts)
#         print(ndt[ndt[:,curr_c]==counts[1][0]])

        curr_c+=1
    res = int("".join(list(map(str, ndt[0]))), 2)
    print(res)
    return res

def co2(dt):
    ndt = dt.copy()
    #print(len(ndt[0]))

    curr_c = 0
    while curr_c<len(dt[0]):

        counts = [sorted(dict(Counter(ndt[:, curr_c])).items(), key=lambda item: item[1])]
        counts = np.array(counts).reshape(-1,2)
        if len(counts)>1:
            if counts[0, 1]== counts[1, 1]:
                ndt = ndt[ndt[:,curr_c]==0]
            else:
                ndt = ndt[ndt[:,curr_c]==counts[0][0]]
        else:
            ndt = ndt[ndt[:,curr_c]==counts[0][0]]

#         print(ndt)
        print(f"Current Col: {curr_c} Rows: {len(ndt)}")
        curr_c+=1
    return int("".join(list(map(str, ndt[0]))), 2)

def part2(inp):
    cs = len(inp[0])
    dt = [int(d) for dt in inp for d in dt]
    dt = np.array(dt).reshape(-1, cs)

    print("O2")
    o2v = o2(dt)
    co2v = co2(dt)
    print(o2v, co2v)
    print(o2v*co2v)
part2(data)

Code seems little bit messy and we could refactor it but I am too busy to do so :(. The test output will be:

O2
Current Col: 0
Current Col: 0 Rows: 7
Current Col: 1
Current Col: 1 Rows: 4
Current Col: 2
Current Col: 2 Rows: 3
Current Col: 3
Current Col: 3 Rows: 2
Current Col: 4
Current Col: 4 Rows: 1
23
Current Col: 0 Rows: 5
Current Col: 1 Rows: 2
Current Col: 2 Rows: 1
Current Col: 3 Rows: 1
Current Col: 4 Rows: 1
23 10
230 

Day 4

Here is the problem link.

Part 1

import numpy as np
data,data1 = get_data(day=4)

def get_blocks(dt):
    block = []
    num = [int(i) for i in dt[0].split(",")]
    row = []
    tdata=[]
    blocks = 0
    for d in dt[2:]:
        if d == "":
            tdata.append(block)
            block=[]
            blocks+=1

        else:
            block.append([int(i) for i in d.strip().split(" ") if i!=""])
    tdata.append(block)
    block=[]
    blocks+=1
    tdata = np.array(tdata).reshape(blocks,-1, 5)
    return tdata, num

def get_first_matched(tdata, num):
    results = np.zeros_like(tdata).astype(np.bool)
    matched = False

    for n in num:
        for i,block in enumerate(tdata):
            results[i] += block==n
            # search across row
            if (results[i]==[ True,  True,  True,  True,  True]).all(axis=1).any():
                print(f"Row Matched Block:{i}")
                matched=True
                break

            # search across cols
            if (results[i].T==[ True,  True,  True,  True,  True]).all(axis=1).any():
                print(f"Col Matched Block: {i}")
                matched=True
                break
        if matched:
            print(f"\nResult Block: {tdata[i]}")
            s = (tdata[i]*~results[i]).sum()
            print(f"Sum: {s}")
            print(f"Last number: {n}")
            print(f"Answer: {n*s}\n")
            break

d1,n1 = get_blocks(data1)
get_first_matched(tdata=d1, num=n1)

# d1, n1

Part 2

def get_last_matched(tdata, num):
    results = np.zeros_like(tdata).astype(np.bool)
    matched = False
    mblocks=[]
    all_blocks = list(range(0, len(results)))

    for n in num:
        for i,block in enumerate(tdata):
            results[i] += block==n
            # search across row
            if (results[i]==[ True,  True,  True,  True,  True]).all(axis=1).any():
                print(f"Row Matched Block:{i}")
                if i not in mblocks:
                    mblocks.append(i)
                if len(mblocks) == len(all_blocks):
                    matched=True

            # search across cols
            if (results[i].T==[ True,  True,  True,  True,  True]).all(axis=1).any():
                print(f"Col Matched Block: {i}")
                if i not in mblocks:
                    mblocks.append(i)
                if len(mblocks) == len(all_blocks):
                    matched=True

        if matched:
            i = mblocks[i]

            print(f"\nResult Block: {tdata[i]}")
            s = (tdata[i]*~results[i]).sum()
            print(f"Sum: {s}")
            print(f"Last number: {n}")
            print(f"Answer: {n*s}")
            break
get_last_matched(tdata=d1, num=n1)

Again, NumPy came to the aid.

Day 5

[Here is the problem link.](https://adventofcode.com/2021/day/5)

Part 1

import numpy as np    
data,data1 = get_data(day=5)

# get(x1, y1, x2, y2)
coordinates = []
for d in data:
    x1, y1, x2, y2 = list(map(int, d.replace(" -> ", ",").split(",")))
    coordinates.append((x1, y1, x2, y2))

coordinates = np.array(coordinates)   
mxx,mxy = coordinates[[0, 2]].max(), coordinates[[1, 3]].max()

board = np.zeros((mxx*2, mxy*2))

# check only horizontal or vertical line
m1 = coordinates[:, 0]==coordinates[:, 2]
m2 = coordinates[:, 1]==coordinates[:, 3]
m = m1 | m2

masked = coordinates[m]  
for co in masked:    
    for x in range(min(co[0], co[2]), max(co[0], co[2])+1):
        for y in range(min(co[1], co[3]), max(co[1], co[3])+1):
            board[x, y] += 1
print((board.flatten()>1).sum())    

The output will be 5 for above code where test data was used. Should use data1 for real output.

Part 2


# diagonal line
m1 = coordinates[:, 0]!=coordinates[:, 2]
m2 = coordinates[:, 1]!=coordinates[:, 3]
m=m1*m2
masked = coordinates[m]

for co in masked:
    # add or sub to x1?
    dx = int(co[2]>co[0]) or -1
    dy = int(co[3]>co[1]) or -1

    for dp in range(abs(co[2]-co[0])+1):
        x = co[0]+dx*dp
        y = co[1]+dy*dp
        board[x,y]+=1

print((board.flatten()>1).sum())    

The output of above code will be 12 for test data.

Day 6

Here is the problem link.

Today's challenge was easy but tricky one. I found 4th day's challenge to be more tough than today's but still I had hard time finding the right way to loop through all days.

Part 1

data,data1 = get_data(day=6)
data = [int(d) for d in data[0].split(",")]
data1 = [int(d) for d in data1[0].split(",")]

days = {}
total_days = 81
curr_data = data1.copy()
for day in range(1, total_days):    
    temp_data = []
    new_fish = []
    for d in curr_data:
        if d == 0:
            new_fish.append(8)
            d=6
        else:
            d-=1
        temp_data.append(d)
    temp_data.extend(new_fish)
    curr_data = temp_data
print(f"Total Fish: {len(curr_data)}\n")

Answer was:

Total Fish: 388419

It took around 2 seconds to run above code while total_days was 81 but when total_day was 257, it seemed like loop will be going on forever. And total fish keeps increasing by time. I even tried to make things faster by using NumPy but it did not work out. Thus, I used dictionaries to store lifespans of fish. Since it could be one of the 0 to 8, why bother keeping lifes?

Part 2

from collections import Counter

lifes = dict(Counter(data1))

days = 256
for day in range(1, days+1):
    lifes = {l: (0 if lifes.get(l+1) is None else lifes.get(l+1)) for l in range(-1, 8)}
    # make all 8s -1 because we create new fish with 8 after it reaches 0
    lifes[8] = lifes[-1]
    # add new lifes to that are exhausted
    lifes[6] += lifes[-1]
    # reset exhausted lifes
    lifes[-1] = 0 

print(sum(lifes.values()))

Day 7

Here is the problem link.

I found today's solution to be easier than previous day's.

Part 1

data,data1 = get_data(day=7)

data = [int(d) for d in data[0].split(",")]
data1 = [int(d) for d in data1[0].split(",")]

l = len(data1)
f = []

for v in range(l):
    f.append((sum([abs(d-v) for d in data1])))
print(min(f))        

One Liner Solution

min([sum([abs(d-v) for d in data1]) for v in range(len(data1))])

Part 2

l = len(data1)
f = []

for v in range(l):
    diff = [abs(d-v) for d in data1]
    diffs = sum([sum(list(range(dif+1))) for dif in diff])
    f.append(diffs)
print(min(f))        

One Liner Solution

min([sum([sum(list(range(abs(d-v)+1))) for d in data1]) for v in range(len(data1))])

Day 8

Here is the problem link.

First part was very easy but for the second part, I took little help from here.

Solution

def permutation(li: list):
    all_ps = set()
    psl = np.prod(np.linspace(1,len(li), len(li)).astype(int))

    while len(all_ps)!=psl:
        curr_ps = np.random.choice(range(len(li)), len(li), replace=False)
        curr_ps = "".join([li[i] for i in curr_ps])
        all_ps.add(curr_ps)
    return all_ps

all_ps = permutation("abcdefg")

d = {
    "abcefg": 0,
    "cf": 1,
    "acdeg": 2,
    "acdfg": 3,
    "bcdf": 4,
    "abdfg": 5,
    "abdefg": 6,
    "acf": 7,
    "abcdefg": 8,
    "abcdfg": 9,
}

cnts = {2:1, 4:4, 3:7, 7:8}

sol1 = 0
sol2 = 0

for row in data1:
    signals, output = row.split("|")
    signals = [s.strip() for s in signals.strip().split(" ")]
    output = [s.strip() for s in output.strip().split(" ")]    

    for o in output:
        l = len(o)
        if ls.get(l):

            sol1+=1

    for pr in all_ps:
        to = str.maketrans("abcdefg", pr)
        ts = ["".join(sorted(sig.translate(to))) for sig in signals]
        top = ["".join(sorted(op.translate(to))) for op in output]

        if all(code in d for code in ts):
            sol2 += int("".join(str(d[code]) for code in top))            
            break
sol1, sol2  

Later I knew there is actually a python generator permutation inside itertools.

Day 9

Here is the problem link.

First part was not much harder to crack but it still took plenty of time. But second part was tricky.

Part 1

import numpy as np
data,data1 = get_data(day=9)

dl = len(data1[0])
dt = np.array([int(d) for dt in data1 for d in dt])
dt = dt.reshape(-1, dl)

nums = []
pos = []
dc = len(dt[0])
dr = len(dt)
for r in range(len(dt)):
    for c in range(len(dt[0])):
        if r==0:
            if c==0:
                if dt[r,c]<dt[r+1, c] and dt[r,c]<dt[r, c+1]:
                    nums.append(dt[r,c])
                    pos.append((r,c))
            elif c==dc-1:
                if dt[r,c]<dt[r+1, c] and dt[r,c]<dt[r, c-1]:
                    nums.append(dt[r,c])
                    pos.append((r,c))
            else:
                if dt[r,c]<dt[r+1, c] and dt[r,c]<dt[r, c+1] and dt[r,c]<dt[r, c-1]:
                    nums.append(dt[r,c])
                    pos.append((r,c))
        elif r==dr-1:
            if c==0:
                if dt[r,c]<dt[r-1, c] and dt[r,c]<dt[r, c+1]:
                    nums.append(dt[r,c])
                    pos.append((r,c))
            elif c==dc-1:
                if dt[r,c]<dt[r-1, c] and dt[r,c]<dt[r, c-1]:
                    nums.append(dt[r,c])
                    pos.append((r,c))
            else:
                if dt[r,c]<dt[r-1, c] and dt[r,c]<dt[r, c+1] and dt[r,c]<dt[r, c-1]:
                    nums.append(dt[r,c])
                    pos.append((r,c))
        else:
            if c==0:
                if dt[r,c]<dt[r-1, c] and dt[r,c]<dt[r, c+1] and dt[r,c]<dt[r+1, c]:
                    nums.append(dt[r,c])
                    pos.append((r,c))
            elif c==dc-1:
                if dt[r,c]<dt[r-1, c] and dt[r,c]<dt[r, c-1] and dt[r,c]<dt[r+1, c]:
                    nums.append(dt[r,c])
                    pos.append((r,c))
            else:
                if dt[r,c]<dt[r-1, c] and dt[r,c]<dt[r, c+1] and dt[r,c]<dt[r, c-1] and dt[r,c]<dt[r+1, c]:
                    nums.append(dt[r,c])
                    pos.append((r,c))

nums

Part 2

I thought I had to use some sort of Searching algorithm like DFS or BFS but I found a solution on StackOverflow using NumPy.

from scipy import ndimage

label, num_label = ndimage.label(dt < 9)
size = np.bincount(label.ravel())

top3 = sorted(size[1:], reverse=True)[:3]
print(np.prod(top3))

Day 10

Here is the problem link.

I forgot the time of the challenge but still managed to make it done. Stack came to the aid.

Part 1

data,data1=get_data(day=10)

table = {
    ")": 3,
    "]": 57,
    "}": 1197,
    ">": 25137}

pair = {"(":")","{":"}", "[":"]", "<":">"}

corruptions = []
rem = []
for i,r in enumerate(data):
    stack = []
    is_corr=False
    for c in r:
        if c in pair:
            stack.append(pair[c])
        elif stack.pop() != c:
            print(f"Corrupted {c} at row {i}")
            corruptions.append(c)
            is_corr=True
            break
    if is_corr==False and len(stack)>0:
        rem.append(stack)

corr = dict(Counter(corruptions))
sum([table[k]*v for k,v in corr.items()])

Part 2

mult = {")": 1,
"]": 2,
"}": 3,
">": 4}
all_total=[]
for row in rem:
    s = 0
    for i,c in enumerate(row):
        s+=5**i*mult[c]
    all_total.append(s)
at = sorted(all_total)
at[len(at)//2]

Day 11

Here is the problem link.

Today's challenge was harder than previous day's.

Solution

adj = [(i,j) for i in range(-1, 2) for j in range(-1,2) if i!=0 or j!=0]
window = {(i,j):darr[i][j] for i in range(10) for j in range(10)}

flashes = 0
i=0
previous = set()

while len(previous)<len(window):
    previous = set()
    window = {k:v+1 for k, v in window.items()}
    while True:
        if sum(v>9 for k,v in window.items() if k not in previous)==0:
            break

        for k,v in window.items():
            if k not in previous and v>9:
                previous.add(k)
                for ad in [(k[0]+i,k[1]+j) for i,j in adj if (k[0]+i,k[1]+j) in window]:
                    window[ad]+=1

    flashes+=len(previous)
    window.update({k:0 for k in previous})
    i+=1
    if i==100:
        print(f"Part 1: {flashes}")

print(f"Part 2: {i}")

Day 12

Here is the problem link.

Due to work I was unable to solve it on time and thus I had to take help from here.

Solution

data,data1 = get_data(day=12)

class Solver:
    def __init__(self, data):
        self.paths = {}
        self.data = data
        self.visited = set()

        self.prepare_paths()
        print(self.solve(part="1"))
        print(self.solve(part="2"))

    def prepare_paths(self):
        for d in self.data:
            l,r = d.split("-")
            if self.paths.get(l):
                self.paths[l].append(r)
            else:
                self.paths[l] = [r]
            if self.paths.get(r):
                self.paths[r].append(l)
            else:
                self.paths[r]=[l]

    def solve(self, curr_cave="start", part="1"):
        if (curr_cave=="end"):
            return 1
        if curr_cave.islower():
            self.visited.add(curr_cave)

        ways_count = sum([self.solve(cave, part) for cave in self.paths[curr_cave] if cave not in self.visited])
        ways_count += 0 if part!="2" else sum([self.solve(cave, cave) for cave in self.paths[curr_cave] if cave in self.visited and cave != "start"])

        if (curr_cave != part): self.visited.discard(curr_cave)
        return ways_count

s = Solver(data1)

Search either BFS or DFS comes into the aid.

Day 13

Here is the problem link.

Today's challenge was fun to do and it was not that hard as well.

Solution

import numpy as np
data1, data = get_data(day=13)

dots = [list(map(int, f.split(","))) for f in data[:data.index("")]]
folds = data[data.index("")+1:]
folds = [f.split("along ")[1].split("=") for f in folds]
folds = [(f[0], int(f[1])) for f in folds]

dots = np.array(dots)
window = np.zeros(dots.max(axis=0)+3)

for c in dots:
    window[c[0], c[1]] = 1
window = window.T

tw = window.copy()
# print(tw)
for f in folds:
    print(f)
    axis,value=f
    cr,cc = tw.shape
    print(tw)
    if axis=="y":
        #fold y axis
        chunk = tw[value+1:-2]
        # print(value-crs,chunk.shape, chunk)
        crs,ccs = chunk.shape
        tw[np.abs(value-crs):value] += chunk[::-1]
        tw = tw[:value]
        tw = np.append(tw, np.zeros((2, tw.shape[1])), axis=0)
        #break

    else:
        # fold x axis
        chunk = tw[:, value+1:-2]
        crs,ccs = chunk.shape
        print(value-crs,chunk.shape, chunk)
        tw[:, abs(value-ccs):value] += chunk[:,::-1]
        tw = tw[:, :value]
        tw = np.append(tw, np.zeros((tw.shape[0], 2)), axis=1)
    print(f"Dots: {np.sum(tw>0)}")

print(np.array2string(tw>0, separator='',
    formatter = {'bool':lambda x: ' █'[x]}))

My answer was:

[[ ██  █  █ ███  ███  ███   ██  █  █ ████   ]
 [█  █ █  █ █  █ █  █ █  █ █  █ █  █    █   ]
 [█  █ ████ █  █ █  █ █  █ █  █ █  █   █    ]
 [████ █  █ ███  ███  ███  ████ █  █  █     ]
 [█  █ █  █ █    █ █  █    █  █ █  █ █      ]
 [█  █ █  █ █    █  █ █    █  █  ██  ████   ]
 [                                          ]
 [                                          ]]

Day 14

Here is the problem link.

They know we could fall into a trap. And again I fell. I went full looping mode and got the result of part 1 but the part 2 could take days.

Part 1

from collections import Counter
data,data1 = get_data(day=14)

wdata=data1.copy()
polymer = wdata[0]
rule = {v[0]:v[1] for v in [d.split(" -> ") for d in wdata[2:]]}

curr_polymer = polymer
i=0
while i< 10:
    tpoly = curr_polymer
#     print(i, tpoly)
    ind = 0
    added = 0
    for k, c in enumerate(tpoly):
        k+=1
        ch = curr_polymer[k-1:k+1]

        mc = rule.get(ch)
        if mc:
            tpoly = [c for c in tpoly]
            tpoly.insert(k+added, mc)
            tpoly = "".join(tpoly)
            added+=1
    curr_polymer = tpoly
    i+=1

res = dict(Counter(curr_polymer))
res = sorted(res.items(), key=lambda x: x[1], reverse=True)
res[0][1]-res[-1][1]

Part 2

Taken hint from here.

tmp_poly = Counter(a+b for a,b in zip(polymer, polymer[1:]))
print(tmp_poly)
chars = Counter(polymer)

for _ in range(40):
    tmp = Counter()
    for (c1,c2),value in tmp_poly.items():
        mc = rule[c1+c2]
        tmp[c1+mc] += value
        tmp[mc+c2] += value
        chars[mc] += value
    tmp_poly=tmp
max(chars.values()) - min(chars.values())

Day 15

Here is the problem link.

Once I failed DSA in my bachelor's degree and I never really understood Graphs and Path Finding but each year Advent of Code makes me try it once. Instead I used something easier than Dijkastra from scratch. Skimage have a way to find Minimum Cost Path

Solution

import numpy as np
from skimage import graph

data,data1 = get_data(15)

data = np.array([int(i) for dt in data for i in dt ]).reshape(-1, len(data[0]))
data
data1 = np.array([int(i) for dt in data1 for i in dt ]).reshape(-1, len(data1[0]))

window = data1.copy()

rs,cs = window.shape

cost = graph.MCP(window, fully_connected=False)
cost.find_costs(starts = [(0,0)])

journey = [window[pos] for pos in  cost.traceback((rs-1,cs-1))[1:]]
print(f"Part1: {sum(journey)}")

# 5times bigger
new_window = window.copy()
nrow = np.hstack([new_window, new_window+1, new_window+2, new_window+3, new_window+4])
new_window = np.vstack([nrow,nrow+1,nrow+2,nrow+3,nrow+4])
rs,cs = new_window.shape

new_window%=9
new_window[new_window==0]=9

cost = graph.MCP(new_window, fully_connected=False)
cost.find_costs(starts = [(0,0)])

journey = [new_window[pos] for pos in  cost.traceback((rs-1,cs-1))[1:]]
print(f"Part2: {sum(journey)}")

Day 16

Here is the problem link.

I was too busy to solve this challenge (but I tried for around 30min) and I did not even want to skip a day so, I had to look over other people's code. The following code is taken from here. All credit goes to the author of this repository.

Part 1

data,data1=get_data(day=16)

data = '''38006F45291200'''.splitlines()
data=data1[0].splitlines()

s = bin(int(data[0], 16))[2:]
n = len(s)
if n % 4 != 0:
    s = '0' * (4 - n % 4) + s
n = len(s)
res = 0
c = 0

while c < n and '1' in s[c:]:
    v = int(s[c: c + 3], 2)
    res += v
    c += 3
    t = int(s[c: c + 3], 2)
    c += 3

    if t == 4:
        num = ''
        while s[c] == '1':
            num += s[c + 1: c + 5]
            c += 5
        num += s[c + 1: c + 5]
        c += 5
        num = int(num, 2)
    else:
        l = int(s[c], 2)
        c += 1
        if l == 0:
            num = int(s[c: c + 15], 2)
            c += 15
        else:
            num = int(s[c: c + 11], 2)
            c += 11

print(res)

Part 2

from functools import reduce

funcDict = {
    0: sum,
    1: lambda a: reduce(lambda x, y: x * y, a),
    2: min,
    3: max,
    5: lambda a: int(a[0] > a[1]),
    6: lambda a: int(a[0] < a[1]),
    7: lambda a: int(a[0] == a[1])
}

def evaluate(u):
    if packets[u][1] == 4:
        return packets[u][2]

    res = []
    for v in graph[u]:
        res.append(evaluate(v))
    return funcDict[packets[u][1]](res)

s = bin(int(data[0], 16))[2:]
for i in data[0]:
    if i != '0':
        break
    s = '0' * 4 + s
n = len(s)
if n % 4 != 0:
    s = '0' * (4 - n % 4) + s
n = len(s)
c = 0
packets = []

while c < n and '1' in s[c:]:
    v = int(s[c: c + 3], 2)
    c += 3
    t = int(s[c: c + 3], 2)
    c += 3

    if t == 4:
        num = ''
        while s[c] == '1':
            num += s[c + 1: c + 5]
            c += 5
        num += s[c + 1: c + 5]
        c += 5
        num = int(num, 2)

        packets.append([v, t, num, c])
    else:
        l = int(s[c], 2)
        c += 1
        if l == 0:
            num = int(s[c: c + 15], 2)
            c += 15
        else:
            num = int(s[c: c + 11], 2)
            c += 11

        packets.append([v, t, l, num, c])

stack = []
graph = [[] for _ in range(len(packets))]

for i, u in enumerate(packets):
    if len(stack) > 0:
        p = stack[-1]
        graph[p].append(i)
        packets[p][3] -= 1
        if packets[p][3] == 0:
            stack.pop()

    while len(stack) > 0:
        p = stack[-1]
        if packets[p][2] == 0 and packets[p][3] <= u[-1] - packets[p][-1]:
            stack.pop()
        else:
            break

    if u[1] != 4:
        stack.append(i)

print(evaluate(0))

Day 17

Here is the problem link.

Part 1

Part 2

Day 18

Here is the problem link.

Part 1

Part 2

Day 19

Here is the problem link.

Part 1

Part 2

Day 20

Here is the problem link.

Part 1

Part 2

Day 21

Here is the problem link.

Part 1

Part 2

Day 22

Here is the problem link.

Part 1

Part 2

Day 23

Here is the problem link.

Part 1

Part 2

Day 24

Here is the problem link.

Part 1

Part 2

Day 25

Here is the problem link.

Part 1

Part 2

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