题目

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

解题思路

1. 从1~num中找平方等于num的值i，找到返回true
2. 如果i²大于num，说明num不是平方数，返回false

代码

func isPerfectSquare(num int) bool {
    
    for i := 1; i <= num; i++ {
        if num == i * i {
            return true 
        } else if num < i * i {
            return false 
        }
    } 
    
    return false 
}