Day3. Start Algorithm

278. First Bad Version/Solution.cs

@@ -0,0 +1,33 @@
+namespace _278._First_Bad_Version;
+
+public class VersionControl
+{
+    protected int _badVersion = 0;
+    protected bool IsBadVersion(int version) => version >= _badVersion;
+}
+
+public class Solution : VersionControl
+{
+    public int FirstBadVersion(int n)
+    {
+        long l = -1;
+        long r = n;
+        while (l != r - 1)
+        {
+            long i = (r + l) / 2;
+            bool res = IsBadVersion((int)i);
+            if (res)
+                r = i;
+            else
+                l = i;
+        }
+        return (int)l + 1;
+    }
+
+    public int FirstBadVersion(int n, int bad)
+    {
+        _badVersion = bad;
+        return FirstBadVersion(n);
+    }
+}
+