Check if a given number is a Perfect square using Binary Search

// C# program to check if a 
// given number is Perfect 
// square using Binary Search 
using System;

class GFG{

// Function to check for 
// perfect square number 
public static int checkPerfectSquare(int N, 
                                     int start,
                                     int last)
{
    // Find the mid value 
    // from start and last 
    int mid = (start + last) / 2;

    if (start > last)
    {
        return -1;
    }

    // Check if we got the number which 
    // is square root of the perfect 
    // square number N 
    if (mid * mid == N)
    {
        return mid;
    }

    // If the square(mid) is greater than N 
    // it means only lower values then mid 
    // will be possibly the square root of N 
    else if (mid * mid > N)
    {
        return checkPerfectSquare(N, start, 
                                  mid - 1);
    }

    // If the square(mid) is less than N 
    // it means only higher values then mid 
    // will be possibly the square root of N 
    else
    {
        return checkPerfectSquare(N, mid + 1,
                                  last);
    }
}

// Driver code 
public static int Main()
{
    int N = 65;

    Console.Write(checkPerfectSquare(N, 1, N));
    return 0;
}
}

// This code is contributed by sayesha