leetcode PowerofFour
z
 2019-04-09 10:36:27   
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public class PowerofFour {
  /**
   * Given an integer (signed 32 bits), write a function to check whether it is a power of 4.
   * 判断一个数是否是4的幂， 4 ^ x = num;
   *
   * Example 1:
   *
   * Input: 16
   * Output: true
   * Example 2:
   *
   * Input: 5
   * Output: false
   * Follow up: Could you solve it without loops/recursion?
   */
  public boolean isPowerOfFour(int num) {
    if (num == 1) return true;
    if (num % 2 == 1) return false;
  while(num % 4 == 0){
    num = num/4;
  }
  if (num != 1){
    return false;
  }
  return true;
  }
}