342. Power of Four

Author: TBXark

342. Power of Four.md

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+# 342. Power of Four
+
+### 2017-03-30
+
+Given an integer (signed 32 bits), write a function to check whether it is a power of 4.
+
+**Example:**
+Given num = 16, return true. Given num = 5, return false.
+
+**Follow up**: Could you solve it without loops/recursion?
+
+
+
+# Solution
+
+```swift
+class Solution {
+ 	func isPowerOfX(x: Int, num: Int) -> Bool {
+         guard num > 0, x > 0 else { return false }
+         let n = log10(Double(num)) / log10(Double(x))
+         return (ceil(n) - n).isZero
+    }
+    func isPowerOfFour(_ num: Int) -> Bool {
+         return isPowerOfX(x: 4, num: num)
+    }
+}
+```
+