1 files changed, 52 insertions, 0 deletions

diff --git a/2020/day5/boarding.py b/2020/day5/boarding.py
new file mode 100644
index 0000000..336cd63
--- /dev/null
+++ b/2020/day5/boarding.py
@@ -0,0 +1,52 @@
+import math
+
+seat_ids = list()
+
+with open("input", "r") as passes:
+
+    for seat in passes:
+        front = 0
+        back = 127
+
+        left = 0
+        right = 7
+
+        for i in seat:
+            if i == "F":
+                back = math.floor((front + back) / 2)
+            elif i == "B":
+                front = math.ceil((front + back) / 2)
+            elif i == "L":
+                right = math.floor((right + left) / 2)
+            else:
+                left = math.ceil((right + left) / 2)
+
+        assert front == back
+        assert left == right
+
+        row = front
+        col = left
+
+        seat_id = row * 8 + col
+
+        seat_ids.append(seat_id)
+
+seat_ids.sort()
+
+# answer to the first part
+print(seat_ids[-1])
+
+# answer to the second part
+lent = len(seat_ids)
+left = 0
+right = lent - 1
+cursor = 0
+
+while right - left > 1:
+    cursor = math.ceil((left + right) / 2)
+    if (seat_ids[left] - left) != (seat_ids[cursor] - cursor):
+        right = cursor
+    elif (seat_ids[right] - right) != (seat_ids[cursor] - cursor):
+        left = cursor
+
+print(seat_ids[cursor] + 1)