Added CPP code for LeetCode question of Power of Four (#365)

Author: paditya99

CPP/PowerOfFour.cpp

@@ -0,0 +1,30 @@
+class Solution {
+public:
+    double value4(double d)
+{
+    return (log2(d))/2;
+}
+bool is_integer(float k)
+{
+  return std::floor(k) == k;
+}
+    bool isPowerOfFour(int n) {
+        if(n<=0){
+            return false;
+        }
+        if(n==1){
+            return true;
+        }
+        if(n%4!=0){
+            return false;
+        }
+        else{
+             if(is_integer(value4(n))){
+        return true;
+    }
+    else{
+        return false;
+    }
+        }
+    }
+};