Add solution for 278-firstBadVersion.

Algorithms/Easy/278_FirstBadVersion/Solution.py

@@ -0,0 +1,23 @@
+# The isBadVersion API is already defined for you.
+# @param version, an integer
+# @return an integer
+# def isBadVersion(version):
+
+class Solution:
+    def firstBadVersion(self, n):
+        """
+        :type n: int
+        :rtype: int
+        """
+        left_version = 1
+        right_version = n
+
+        while left_version < right_version:
+            mid_version = (left_version + right_version)//2
+
+            if isBadVersion(mid_version):
+                right_version = mid_version
+            else:
+                left_version = mid_version + 1
+
+        return left_version