diff --git a/aoc2020/Pipfile b/aoc2020/Pipfile
index 3b066fa..5518735 100644
--- a/aoc2020/Pipfile
+++ b/aoc2020/Pipfile
@@ -7,6 +7,7 @@ name = "pypi"
 
 [dev-packages]
 mypy = ""
+pytest = ""
 
 [requires]
 python_version = "3.9"
diff --git a/aoc2020/Pipfile.lock b/aoc2020/Pipfile.lock
index d873b66..325e836 100644
--- a/aoc2020/Pipfile.lock
+++ b/aoc2020/Pipfile.lock
@@ -1,7 +1,7 @@
 {
     "_meta": {
         "hash": {
-            "sha256": "752181fd1aaa6cf905a654df10d56863fe61b74b26e95802148d225644e9bc5a"
+            "sha256": "ed02d1728cc686824535903ae2f5f3956ba104434c4c6e532237df55bcd69a12"
         },
         "pipfile-spec": 6,
         "requires": {
@@ -17,6 +17,21 @@
     },
     "default": {},
     "develop": {
+        "attrs": {
+            "hashes": [
+                "sha256:31b2eced602aa8423c2aea9c76a724617ed67cf9513173fd3a4f03e3a929c7e6",
+                "sha256:832aa3cde19744e49938b91fea06d69ecb9e649c93ba974535d08ad92164f700"
+            ],
+            "markers": "python_version >= '2.7' and python_version not in '3.0, 3.1, 3.2, 3.3'",
+            "version": "==20.3.0"
+        },
+        "iniconfig": {
+            "hashes": [
+                "sha256:011e24c64b7f47f6ebd835bb12a743f2fbe9a26d4cecaa7f53bc4f35ee9da8b3",
+                "sha256:bc3af051d7d14b2ee5ef9969666def0cd1a000e121eaea580d4a313df4b37f32"
+            ],
+            "version": "==1.1.1"
+        },
         "mypy": {
             "hashes": [
                 "sha256:0a0d102247c16ce93c97066443d11e2d36e6cc2a32d8ccc1f705268970479324",
@@ -45,6 +60,55 @@
             ],
             "version": "==0.4.3"
         },
+        "packaging": {
+            "hashes": [
+                "sha256:24e0da08660a87484d1602c30bb4902d74816b6985b93de36926f5bc95741858",
+                "sha256:78598185a7008a470d64526a8059de9aaa449238f280fc9eb6b13ba6c4109093"
+            ],
+            "markers": "python_version >= '2.7' and python_version not in '3.0, 3.1, 3.2, 3.3'",
+            "version": "==20.8"
+        },
+        "pluggy": {
+            "hashes": [
+                "sha256:15b2acde666561e1298d71b523007ed7364de07029219b604cf808bfa1c765b0",
+                "sha256:966c145cd83c96502c3c3868f50408687b38434af77734af1e9ca461a4081d2d"
+            ],
+            "markers": "python_version >= '2.7' and python_version not in '3.0, 3.1, 3.2, 3.3'",
+            "version": "==0.13.1"
+        },
+        "py": {
+            "hashes": [
+                "sha256:21b81bda15b66ef5e1a777a21c4dcd9c20ad3efd0b3f817e7a809035269e1bd3",
+                "sha256:3b80836aa6d1feeaa108e046da6423ab8f6ceda6468545ae8d02d9d58d18818a"
+            ],
+            "markers": "python_version >= '2.7' and python_version not in '3.0, 3.1, 3.2, 3.3'",
+            "version": "==1.10.0"
+        },
+        "pyparsing": {
+            "hashes": [
+                "sha256:c203ec8783bf771a155b207279b9bccb8dea02d8f0c9e5f8ead507bc3246ecc1",
+                "sha256:ef9d7589ef3c200abe66653d3f1ab1033c3c419ae9b9bdb1240a85b024efc88b"
+            ],
+            "markers": "python_version >= '2.6' and python_version not in '3.0, 3.1, 3.2, 3.3'",
+            "version": "==2.4.7"
+        },
+        "pytest": {
+            "hashes": [
+                "sha256:1969f797a1a0dbd8ccf0fecc80262312729afea9c17f1d70ebf85c5e76c6f7c8",
+                "sha256:66e419b1899bc27346cb2c993e12c5e5e8daba9073c1fbce33b9807abc95c306"
+            ],
+            "index": "pypi",
+            "markers": "python_version >= '3.6'",
+            "version": "==6.2.1"
+        },
+        "toml": {
+            "hashes": [
+                "sha256:806143ae5bfb6a3c6e736a764057db0e6a0e05e338b5630894a5f779cabb4f9b",
+                "sha256:b3bda1d108d5dd99f4a20d24d9c348e91c4db7ab1b749200bded2f839ccbe68f"
+            ],
+            "markers": "python_version >= '2.6' and python_version not in '3.0, 3.1, 3.2, 3.3'",
+            "version": "==0.10.2"
+        },
         "typed-ast": {
             "hashes": [
                 "sha256:07d49388d5bf7e863f7fa2f124b1b1d89d8aa0e2f7812faff0a5658c01c59aa1",
diff --git a/aoc2020/day05/solution.py b/aoc2020/day05/solution.py
new file mode 100644
index 0000000..c881605
--- /dev/null
+++ b/aoc2020/day05/solution.py
@@ -0,0 +1,77 @@
+import sys
+import typing
+
+
+def main() -> int:
+    highest_seat = 0
+
+    taken_seats = set()
+
+    for line in sys.stdin:
+        line = line.strip()
+        if line == "":
+            continue
+
+        seat = _locate_seat(line)
+
+        if seat.number > highest_seat:
+            highest_seat = seat.number
+
+        taken_seats.add(seat.number)
+
+        print(f"bp={line} row={seat.row} column={seat.col} seat={seat.number}")
+
+    seat_number: typing.Optional[int] = None
+    n_found = 0
+
+    for candidate_seat in range(0, (127 * 8) + 1):
+        if candidate_seat in taken_seats:
+            continue
+
+        if (candidate_seat - 1) in taken_seats and (candidate_seat + 1) in taken_seats:
+            seat_number = candidate_seat
+            n_found += 1
+
+    print(f"highest_seat={highest_seat} seat_number={seat_number} n_found={n_found}")
+
+    return 0
+
+
+class Seat:
+    row: int
+    column: int
+
+    def __init__(self, row: int = 0, col: int = 0):
+        self.row = row
+        self.col = col
+
+    @property
+    def number(self) -> int:
+        return (self.row * 8) + self.col
+
+
+def _locate_seat(bp: str) -> Seat:
+    rows = list(range(0, 128))
+    cols = list(range(0, 8))
+
+    row_part = list(bp[:7])
+    col_part = list(bp[7:])
+
+    return Seat(
+        row=_bisect(rows, [{"F": 0, "B": 1}[s] for s in row_part]),
+        col=_bisect(cols, [{"L": 0, "R": 1}[s] for s in col_part]),
+    )
+
+
+def _bisect(initial_selection: typing.List[int], bisections: typing.List[int]) -> int:
+    selection = initial_selection[:]
+
+    for bisection in bisections:
+        halfway = int(len(selection) / 2)
+        selection = [selection[:halfway], selection[halfway:]][bisection]
+
+    return selection[0]
+
+
+if __name__ == "__main__":
+    sys.exit(main())
diff --git a/aoc2020/day05/test-input b/aoc2020/day05/test-input
new file mode 100644
index 0000000..b036d3e
--- /dev/null
+++ b/aoc2020/day05/test-input
@@ -0,0 +1,3 @@
+BFFFBBFRRR
+FFFBBBFRRR
+BBFFBBFRLL
diff --git a/aoc2020/day05/test-output b/aoc2020/day05/test-output
new file mode 100644
index 0000000..3f39075
--- /dev/null
+++ b/aoc2020/day05/test-output
@@ -0,0 +1,3 @@
+bp=BFFFBBFRRR row=70 column=7 seat=567
+bp=FFFBBBFRRR row=14 column=7 seat=119
+bp=BBFFBBFRLL row=102 column=4 seat=820
diff --git a/aoc2020/day05/test_solution.py b/aoc2020/day05/test_solution.py
new file mode 100644
index 0000000..9d6a571
--- /dev/null
+++ b/aoc2020/day05/test_solution.py
@@ -0,0 +1,23 @@
+import sys
+
+from pathlib import Path
+
+import pytest
+
+from solution import main
+
+
+HERE = Path(__file__).absolute().parent
+
+
+def test_solution(capsys):
+    with (HERE / "test-input").open() as infile:
+        sys.stdin = infile
+        main()
+
+    expected_output = (HERE / "test-output").read_text().splitlines()
+    assert expected_output == [
+        l
+        for l in capsys.readouterr().out.splitlines()
+        if not l.startswith("highest_seat")
+    ]