Shortest way to check perfect Square?

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What's a good algorithm to determine if an input is a perfect square?

I want Shortest and Simplest way to Check a number is perfect square in C#

Some of Perfect Squares:

1, 4, 9, 16, 25, 36, 49, 64, 81, 100, ......

Answer 1

Probably checking if the square root of the number has any decimal part, or if it is a whole number.

Implementationwise, I would consider something like this:

double result = Math.Sqrt(numberToCheck);
bool isSquare = result%1 == 0;

isSquare should now be true for all squares, and false for all others.

Answer 2

public bool IsPerfectSquare(int num)
{
   int root = (int)Math.Sqrt(num);
   return (int) Math.Pow(root,2) == num;
}

Answer 3

This is a variant on checking if the square root is integral:

bool IsPerfectSquare(double input)
{
    var sqrt = Math.Sqrt(input);
    return Math.Abs(Math.Ceiling(sqrt) - Math.Floor(sqrt)) < Double.Epsilon;
}

Math.Ceiling will round up to the next integer, whereas Math.Floor will round down. If they are the same, well, then you have an integer!

This can also be written as a oneliner:

if (int(Math.Ceiling(Math.Sqrt(n))) == int(Math.Floor(Math.Sqrt(n)))) /* do something */;

Answer 4

    public bool IsPerferctSquare(uint number)
    {
        return (Math.Sqrt(number) % 1 == 0);
    }