ValidPerfectSquareSln.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace BinarySearch.Lib
{
    //    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
    public class ValidPerfectSquareSln
    {
        public bool IsPerfectSquare(int num)
        {
            int low = 1, high = num;
            while (low <= high)
            {
                long mid = (low + high) >> 1;
                if (mid * mid == num)
                {
                    return true;
                }
                else if (mid * mid < num)
                {
                    low = (int)mid + 1;
                }
                else
                {
                    high = (int)mid - 1;
                }
            }
            return false;
        }

    }
}