add cpp solution

Author: jinshendan

June-LeetCoding-Challenge/08-Power-Of-Two/Power-Of-Two.cpp

@@ -0,0 +1,8 @@
+class Solution {
+public:
+    bool isPowerOfTwo(int n) {
+        long long x = n;
+        if (x == 0) return false;
+        return (x & (-x)) == x;
+    }
+};