From 074c48b33e3b4fa31e0cdfba357e727fe18f2a5f Mon Sep 17 00:00:00 2001
From: Brian Chu <brianmchu42@gmail.com>
Date: Tue, 7 Dec 2021 22:22:29 -0800
Subject: solution for day 8

---
 day8.py | 61 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 61 insertions(+)
 create mode 100644 day8.py

diff --git a/day8.py b/day8.py
new file mode 100644
index 0000000..b78bd1a
--- /dev/null
+++ b/day8.py
@@ -0,0 +1,61 @@
+#!/usr/bin/env python
+
+with open("day8.txt") as data:
+    signals, outputs = [], []
+    for line in data:
+        signal, output = line.strip().split('|')
+        signal, output = signal.strip().split(), output.strip().split()
+        signals.append(signal)
+        outputs.append(output)
+# part 1
+total = 0
+for output in outputs:
+    for digit in output:
+        match len(digit):
+            case 2 | 3 | 4 | 7:
+                total += 1
+            case _:
+                continue
+print(total)
+
+# part 2
+
+def lookup(signalmap):
+    inverted = {frozenset(v): str(k) for k, v in signalmap.items()}
+    def lookup_func(signals):
+        return inverted[frozenset(signals)]
+    return lookup_func
+
+total = 0
+for signal, output in zip(signals, outputs):
+    # determine what goes where
+    signalmap = {}
+    signal.sort(key=lambda x: len(x))
+    signalmap[1] = set(signal[0]) # 2 segments
+    signalmap[7] = set(signal[1]) # 3 segments
+    signalmap[4] = set(signal[2]) # 4 segments
+    signalmap[8] = set(signal[9]) # 7 segments
+
+    # 5 segments: 2, 3, 5
+    for digit in map(set, signal[3:6]):
+        if signalmap[1].issubset(digit):
+            signalmap[3] = digit
+        elif len(digit & signalmap[4]) == 2:
+            signalmap[2] = digit
+        elif len(digit & signalmap[4]) == 3:
+            signalmap[5] = digit
+    # 6 segments: 0, 6, 9
+    for digit in map(set, signal[6:9]):
+        if signalmap[4].issubset(digit):
+            signalmap[9] = digit
+        elif signalmap[1].issubset(digit):
+            signalmap[0] = digit
+        elif len(signalmap[1] & digit) == 1:
+            signalmap[6] = digit
+
+    lookup_func = lookup(signalmap)
+    # decode output
+    out_string = "".join(lookup_func(x) for x in output)
+    total += int(out_string)
+
+print(total)
-- 
cgit 1.4.1-2-gfad0