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@pawlos /advent_of_code_d14.py Secret
Last active Dec 20, 2017

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Solution to Day 14: Disk Defragmentation
#aoc_d14.py
def knot_hash(inputstr):
skip_size = 0
inp = range(0,256)
ind = 0
for i in range(0,64):
lengths = [ord(c) for c in inputstr]
add = [17, 31, 73, 47, 23]
lengths = lengths + add
#print lengths
for l in lengths:
w = []
for i in range(ind,ind+l):
w.append(inp[i%len(inp)])
rev = w[::-1]
o = {}
for i in range(ind,ind+l):
o[i%len(inp)] = rev[i-ind]
n = [None]*len(inp)
for i in range(0,len(inp)):
if i in o:
n[i]= o[i]
else:
n[i] = inp[i]
inp = n
ind = (ind + (l + skip_size)) % len(inp)
skip_size += 1
res = ''
for i in range(0,16):
w = inp[i*16:(i+1)*16]
z = w[0]
for r in range(1,len(w)):
z = z ^ w[r]
res += '{:02x}'.format(z)
return res
sum_bits = 0
for i in range(128):
r = knot_hash("stpzcrnm-"+str(i))
sum_bits += bin(int(r,16)).count("1")
print i,r, sum_bits
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