p342

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LeetCode p342 Power of Four 题解

1.题目：

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?

题意：

判断一个数是否为4的n次方

2.解题思路:

见代码，枚举。

3.代码

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public class Solution {
    public boolean isPowerOfFour(int num) {
        List<Integer> list = new ArrayList<Integer>();
		int sum = 1;
		for (int i = 1; i < 17; i++) {
			list.add(sum);
			sum = sum * 4;

		}
		if (list.contains(num))
			return true;
		return false;
    }
}

4.一些总结：