day 8 part 1 (C) + init part 2

2021/day08/README.txt

@@ -69,3 +69,62 @@ fgae cfgab fg bagce
 Because the digits 1, 4, 7, and 8 each use a unique number of segments, you should be able to tell which combinations of signals correspond to those digits. Counting only digits in the output values (the part after | on each line), in the above example, there are 26 instances of digits that use a unique number of segments (highlighted above).
 
 In the output values, how many times do digits 1, 4, 7, or 8 appear?
+
+Your puzzle answer was 543.
+
+The first half of this puzzle is complete! It provides one gold star: *
+--- Part Two ---
+
+Through a little deduction, you should now be able to determine the remaining digits. Consider again the first example above:
+
+acedgfb cdfbe gcdfa fbcad dab cefabd cdfgeb eafb cagedb ab |
+cdfeb fcadb cdfeb cdbaf
+
+After some careful analysis, the mapping between signal wires and segments only make sense in the following configuration:
+
+ dddd
+e    a
+e    a
+ ffff
+g    b
+g    b
+ cccc
+
+So, the unique signal patterns would correspond to the following digits:
+
+    acedgfb: 8
+    cdfbe: 5
+    gcdfa: 2
+    fbcad: 3
+    dab: 7
+    cefabd: 9
+    cdfgeb: 6
+    eafb: 4
+    cagedb: 0
+    ab: 1
+
+Then, the four digits of the output value can be decoded:
+
+    cdfeb: 5
+    fcadb: 3
+    cdfeb: 5
+    cdbaf: 3
+
+Therefore, the output value for this entry is 5353.
+
+Following this same process for each entry in the second, larger example above, the output value of each entry can be determined:
+
+    fdgacbe cefdb cefbgd gcbe: 8394
+    fcgedb cgb dgebacf gc: 9781
+    cg cg fdcagb cbg: 1197
+    efabcd cedba gadfec cb: 9361
+    gecf egdcabf bgf bfgea: 4873
+    gebdcfa ecba ca fadegcb: 8418
+    cefg dcbef fcge gbcadfe: 4548
+    ed bcgafe cdgba cbgef: 1625
+    gbdfcae bgc cg cgb: 8717
+    fgae cfgab fg bagce: 4315
+
+Adding all of the output values in this larger example produces 61229.
+
+For each entry, determine all of the wire/segment connections and decode the four-digit output values. What do you get if you add up all of the output values?