题目描述：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: 16Returns: TrueExample 2:Input: 14Returns: False本题属于数学分类。思路：任意完全平方数可通过1+3+5...+K的和得到。实现代码：
public class Solution { public bool IsPerfectSquare(int num) { var start = 1; while(num > 0){ num -= start; start += 2; } return num == 0; }}
