Square Count: Challenge

Create a program that will count the number of perfect square numbers between 0 and 100. A perfect square is a number that is the product of a rational number multiplied by itself. For example, 9 is a perfect square (3*3), and so is 25 (5*5).

Start by creating a new C# project, then follow the steps below.

IsSquare method

Copy the following method into your program. It will take in an int, and return a bool that says whether or not the integer is a perfect square.

public static bool IsSquare(int num)
{
    double sqrt = Math.Sqrt(num);
    return sqrt == Math.Floor(sqrt);
}

Finding the squares

1. In the Main method, declare a new List<int> variable named squares
2. Initialize the value of squares to a new empty list
3. Create a for loop that will iterate through the numbers 0-100
   • for keyword
   • initializer (use i as the variable)
   • condition
   • increment
4. In the body of the for loop, use an if statement to check whether the current number (i) is a square
   • Pass i as an argument to the IsSquare method
5. If i is a square, Add it to the squares list

Printing the count

1. In the body of the Main method, beneath the for loop, find the Count of the squares list
2. Store the count in a variable
3. Display a message to the user informing them of the count

Try running the program. It should have a count of 11. If the count says 10, there may be an off-by-one error!

Squaring a number

One interesting side effect for this list of perfect squares is that each item in the list is the square of its own index. For example, the item at index 0 in the list is 0, the item at index 4 in the list is 16, and so on. It is possible to use this list to calculate squares without having to do the math!

1. In the body of the Main method, beneath the count message, display a message asking the user which number they would like to square
2. Store the number they enter as an int variable (num)
3. Declare a new variable that will hold the number squared
4. Set the variable to the item in the squares list at position num
5. Display a message to the user telling them the square value
   • Ex. If they enter 6, "6 squared is 36"

Extra Challenges

Custom limit

Instead of counting all the squares from 0-100, allow the user to enter the upper limit. Use the number they enter in the for loop instead of 100.

Better error handling

When squaring a number, do not allow the user to square a number outside the range of the list. For example, if they wish to square the number 20, but there fewer than 21 items in the list, display a message saying "Number not within range."