My Advent of Code solutions in Python.
kevinyap.ca/2019/12/going-fast-in-advent-of-code/
advent-of-code
python
Add solution for 2019/16
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+40
2019/day16.py
+40
2019/day16.py
···
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import fileinput
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PATTERN = [0, 1, 0, -1]
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SIGNAL = [int(s) for s in fileinput.input()[0].strip()]
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def fft(signal):
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def coeff(idx, digit):
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r = ((idx + 1) // (digit + 1)) % 4
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return PATTERN[r]
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for _ in range(100):
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for i in range(len(signal)):
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res = 0
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for j, d in enumerate(signal):
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res += coeff(j, i) * d
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signal[i] = abs(res) % 10
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return signal
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def fft_backhalf(signal):
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# What pattern?
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for _ in range(100):
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partial = 0
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for i in reversed(range(len(signal) // 2, len(signal))):
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partial += signal[i]
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signal[i] = partial % 10
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return signal
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part_1 = ''.join(str(n) for n in fft(SIGNAL[:]))[:8]
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print "First 8 digits of FFT(input):", part_1
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offset = int(''.join(str(n) for n in SIGNAL[:7]))
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part_2 = ''.join(str(n) for n in fft_backhalf(SIGNAL * 10000)[offset:offset+8])
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print "Offset digits of FFT(input * 10000):", part_2
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2019/inputs/16.txt
+1
2019/inputs/16.txt
···
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59709511599794439805414014219880358445064269099345553494818286560304063399998657801629526113732466767578373307474609375929817361595469200826872565688108197109235040815426214109531925822745223338550232315662686923864318114370485155264844201080947518854684797571383091421294624331652208294087891792537136754322020911070917298783639755047408644387571604201164859259810557018398847239752708232169701196560341721916475238073458804201344527868552819678854931434638430059601039507016639454054034562680193879342212848230089775870308946301489595646123293699890239353150457214490749319019572887046296522891429720825181513685763060659768372996371503017206185697