From 730596f4163ee804364cc6f61a0dd34f94c8fe90 Mon Sep 17 00:00:00 2001
From: Johan Sandoval <jojo.han718@gmail.com>
Date: Wed, 22 Jul 2026 21:02:15 -0500
Subject: [PATCH] Finish problem 0278-first-bad-version

---
 problems/0278-first-bad-version/solution.py     | 14 ++++++++++++++
 .../0278-first-bad-version/solution_test.py     | 17 +++++++++++++++++
 2 files changed, 31 insertions(+)
 create mode 100644 problems/0278-first-bad-version/solution.py
 create mode 100644 problems/0278-first-bad-version/solution_test.py

diff --git a/problems/0278-first-bad-version/solution.py b/problems/0278-first-bad-version/solution.py
new file mode 100644
index 0000000..a63bcfb
--- /dev/null
+++ b/problems/0278-first-bad-version/solution.py
@@ -0,0 +1,14 @@
+def isBadVersion(version: int) -> bool:
+    raise NotImplementedError
+
+
+class Solution:
+    def firstBadVersion(self, n: int) -> int:
+        lo, hi = 1, n
+        while lo < hi:
+            check = (hi + lo) // 2
+            if isBadVersion(check):
+                hi = check
+            else:
+                lo = check + 1
+        return lo
diff --git a/problems/0278-first-bad-version/solution_test.py b/problems/0278-first-bad-version/solution_test.py
new file mode 100644
index 0000000..19a7b33
--- /dev/null
+++ b/problems/0278-first-bad-version/solution_test.py
@@ -0,0 +1,17 @@
+import pytest
+import solution
+from solution import Solution
+
+
+@pytest.mark.parametrize(
+    "n,bad",
+    [
+        (5, 4),
+        (1, 1),
+        (10, 1),
+        (10, 10),
+    ],
+)
+def test_first_bad_version(n, bad, monkeypatch):
+    monkeypatch.setattr(solution, "isBadVersion", lambda v: v >= bad)
+    assert Solution().firstBadVersion(n) == bad