power of three

fishercoder1534 · fishercoder1534 · commit a87a7d8cdbbd · 2016-08-07T18:33:29.000-07:00
diff --git a/EASY/src/easy/PowerOfThree.java b/EASY/src/easy/PowerOfThree.java
@@ -0,0 +1,41 @@
+package easy;
+/**326. Power of Three  QuestionEditorial Solution  My Submissions
+Total Accepted: 57555
+Total Submissions: 151383
+Difficulty: Easy
+Given an integer, write a function to determine if it is a power of three.
+
+Follow up:
+Could you do it without using any loop / recursion?
+
+*/
+
+public class PowerOfThree {
+    //it turns out they're using a trick to solve this question without using a loop: find the max possible integer that is a power of 3, then do modulor with this number
+    public boolean isPowerOfThree_without_loop(int n) {
+        return (n > 0 && 1162261467 % n == 0);
+    }
+    
+//I'm not able to think of a method that has no loop to do it, use regular method to solve it first
+    public boolean isPowerOfThree(int n) {
+        if(n < 3 && n != 1) return false;
+        while(n != 1){
+            if(n%3 != 0) return false;
+            n /= 3;
+        }
+        return true;
+    }
+    
+    public static void main(String...strings){
+        PowerOfThree test = new PowerOfThree();
+        System.out.println(test.isPowerOfThree(12));
+        
+        //find the max integer that is power of 3
+        int maxPowerOf3_one_step_further = 3, maxPowerOf3 = 0;
+        while(maxPowerOf3_one_step_further >= 0){
+            maxPowerOf3_one_step_further = (int) maxPowerOf3_one_step_further*3;
+            if(maxPowerOf3_one_step_further > 0) maxPowerOf3 = maxPowerOf3_one_step_further;
+            System.out.println("maxPowerOf3 is: " + maxPowerOf3);
+        }
+    }
+}
