Day 6

2019/day6.py

@@ -0,0 +1,42 @@
+def main():
+    with open("day6.txt", "rt") as input_file:
+        lines = input_file.readlines()
+    entries = [tuple(line.rstrip().split(")")) for line in lines]
+    orbit_map = build_map(entries)
+    
+    # Part 1
+    num_orbits = sum(count_orbits(orbit_map, s) for s in orbit_map.keys())
+    print("Num orbits:", num_orbits)
+
+    # Part 2
+    you_cursor, san_cursor = orbit_map["YOU"], orbit_map["SAN"]
+    you_way, san_way = [], []
+    jumps = 0
+    while you_cursor is not None or san_cursor is not None:
+        you_cursor = orbit_map.get(you_cursor)
+        san_cursor = orbit_map.get(san_cursor)
+        you_way.append(you_cursor)
+        san_way.append(san_cursor)
+        if you_cursor in san_way:
+            jumps = san_way.index(you_cursor) + len(you_way)
+            break
+        if san_cursor in you_way:
+            jumps = you_way.index(san_cursor) + len(san_way)
+            break
+    print("Required jumps:", jumps + 1)
+
+def build_map(entries):
+    orbit_map = {}
+    for center, satellite in entries:
+        orbit_map[satellite] = center
+    return orbit_map
+
+def count_orbits(orbit_map, satellite):
+    if satellite in orbit_map:
+        return 1 + count_orbits(orbit_map, orbit_map[satellite])
+    else:
+        return 0
+
+
+if __name__ == "__main__":
+    main()