Solve 278 with C++.

Author: illuz

solutions/278.First_Bad_Version/AC_binary_search_logn.cpp

@@ -0,0 +1,39 @@
+/*
+*  Author:      illuz <iilluzen[at]gmail.com>
+*  File:        AC_binary_search_logn.cpp
+*  Create Date: 2015-09-24 09:33:56
+*  Descripton:   
+*/
+
+#include <bits/stdc++.h>
+
+using namespace std;
+const int N = 0;
+
+// Forward declaration of isBadVersion API.
+bool isBadVersion(int version) { return version >= 1; }
+
+class Solution {
+public:
+    int firstBadVersion(int n) {
+        int l = 1, r = n;
+        while (l < r) {
+            int mid = l + (r - l) / 2;
+            if (isBadVersion(mid)) {
+                r = mid;
+            } else {
+                l = mid + 1;
+            }
+        }
+        return l;
+    }
+};
+
+int main() {
+    int n;
+    Solution s;
+    cin >> n;
+    cout << s.firstBadVersion(n) << endl;
+    return 0;
+}
+