题意:判断1个数n是否刚好是2的幂,幂大于0. 思路:注意会给负数,奇数.对于每个数判断31次即可. class Solution { public: bool isPowerOfTwo(int n) { ||(n&)==&&n>) return false; unsigned ; while(t<n) //注意爆int t<<=; if(t==n) return true; return false; } }; AC代码 一行代码,更巧的写法: 如果一个数…

问题 该文章的最新版本已迁移至个人博客[比特飞],单击链接 https://www.byteflying.com/archives/4058 访问. 给定一个整数 (32 位有符号整数),请编写一个函数来判断它是否是 4 的幂次方. 输入: 16 输出: true 输入: 5 输出: false 进阶:你能不使用循环或者递归来完成本题吗? Given an integer (signed 32 bits), write a function to check whether it is a po…

问题 该文章的最新版本已迁移至个人博客[比特飞],单击链接 https://www.byteflying.com/archives/3867 访问. 给定一个整数,写一个函数来判断它是否是 3 的幂次方. 输入: 27 输出: true 输入: 0 输出: false 输入: 9 输出: true 输入: 45 输出: false 进阶:你能不使用循环或者递归来完成本题吗? Given an integer, write a function to determine if it is a po…

问题 该文章的最新版本已迁移至个人博客[比特飞],单击链接 https://www.byteflying.com/archives/3858 访问. 给定一个整数,编写一个函数来判断它是否是 2 的幂次方. 输入: 1 输出: true 解释: 20 = 1 输入: 16 输出: true 解释: 24 = 16 输入: 218 输出: false Given an integer, write a function to determine if it is a power of two. C…

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? Credits:Special thanks to @yukuairoy fo…

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? Credits:Special thanks to @dietpepsi for adding this problem and creating all test cases. 这道题让我们判断一个数是不是3的次方数,在Le…

Given an integer, write a function to determine if it is a power of two. Hint: Could you solve it in O(1) time and using O(1) space? 这道题让我们判断一个数是否为2的次方数,而且要求时间和空间复杂度都为常数,那么对于这种玩数字的题,我们应该首先考虑位操作 Bit Operation.在LeetCode中,位操作的题有很多,比如比如Repeated DNA Seque…

Given an integer, write a function to determine if it is a power of two. 题目意思: 给定一个整数,判断是否是2的幂 解题思路: 如果一个整数是2的幂,则二进制最高位为1,减去1后则最高位变为0,后面全部是1,相与判读是否为零,注意负数和0,负数的最高位是1. 更多二进制的问题可以参考<编程之美>中二进制有多少个1,面试时容易问. 源代码: class Solution { public: bool isPowerOfTw…

原题链接在这里:https://leetcode.com/problems/power-of-four/ 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…

原题链接在这里:https://leetcode.com/problems/power-of-three/ 与Power of Two类似.检查能否被3整除,然后整除,再重复检查结果. Time Complexity: O(logn). n是原始数字.Space: O(1). AC Java: public class Solution { public boolean isPowerOfThree(int n) { if(n < 1){ return false; } while(n > 1…