Check if a given number is a perfect square with only addition or substraction operation. eg. 25 returns true; 19 returns false. Perfect square number 有一个特性,比如0,1,4,9,16,25 他们之间的间隔分别是1,3,5,7,9,每次间隔都是i+2. 所以每次往下减i, i 更新成i+2. 看最后结果是否为0即可. import java.u…

Given a positive integer num, write a function which returns True if num is a perfect square else False. Note: Do not use any built-in library function such as sqrt. Example 1: Input: 16 Returns: True Example 2: Input: 14 Returns: False Credits:Speci…

Given a positive integer num, write a function which returns True if num is a perfect square else False. Note: Do not use any built-in library function such as sqrt. Example 1: Input: 16 Returns: True Example 2: Input: 14 Returns: False 本题可以用binary s…

这道题首先想到的算法是DP.每个perfect square number对应的解都是1.先生成一个n+1长的DP list.对于每个i,可以用dp[i] = min(dp[j] + dp[i-j], dp[i])来更新,这里j 是<= i 的一个perfect square number.但是DP的算法超时. class Solution(object): def numSquares(self, n): """ :type n: int :rtype: int &q…

Given a positive integer num, write a function which returns True if num is a perfect square else False. Note: Do not use any built-in library function such as sqrt. Example 1: Input: 16 Returns: True Example 2: Input: 14 Returns: False 分析:二分.注意溢出! p…

题目描述: Given a positive integer num, write a function which returns True if num is a perfect square else False. 解题分析: 这种找数字的题一般都用类似与二分查找的算法.需要注意的是比较平方和时考虑到integer溢出的情况.所以这个结果是要用Long类型保存.由此到来的改变是判断相等时要用“equals()”方法,而不是“==”. 实现代码: public class Solution…

Given a positive integer num, write a function which returns True if num is a perfect square else False. Note: Do not use any built-in library function such as sqrt. Example 1: Input: 16 Output: true Example 2: Input: 14 Output: false 给定一个正整数 num,编写一…

原题: 367. Valid Perfect Square 读题: 求一个整数是否为完全平方数,如1,4,9,16,……就是完全平方数,这题主要是运算效率问题 求解方法1:812ms class Solution { public: bool isPerfectSquare(int num) { if(num < 0) return false; int i = 0; //这里要加1,不然num = 1时会出错 for(;i< num/2 + 1;i++) { if(i*i == num) {…

Given a positive integer num, write a function which returns True if num is a perfect square else False. Note: Do not use any built-in library function such as sqrt. Example 1: Input: 16 Output: true Example 2: Input: 14 Output: false 想法:完全平方数是等差数列相加…

Given a positive integer num, write a function which returns True if num is a perfect square else False. Note: Do not use any built-in library function such as sqrt. Example 1: Input: 16 Returns: True Example 2: Input: 14 Returns: False 题意: 验证完全平方数 思…