leetcode-367-valid-perfect-square.swift

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https://leetcode.com/problems/valid-perfect-square/


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

*/

/**
Big O Annotation
Time complexity O(n) where n is the elements between 0 and num.
Space complexity O(1) where only using constant space.
*/
func isPerfectSquare(_ num: Int) -> Bool {
        
    // Iterate from 0 up to including num
    for number in 0...num {
        
        // Get the square of the current number
        let numberSquared = number * number
        
        /**
        If that squared number of larger 
        or equal to num,
        check if it is num and 
        return true if so, false otherwise
        */
        if numberSquared >= num {
            return numberSquared == num
        }
    }
    return false
}