CODEWITHSUNDEEP
c#
Moosa Raza
Moosa Raza

Reputation: 107

Not able to calculate the correct product of Pythagorean triplet from the sum of the triplets

A Pythagorean triplet is a set of three natural number, a < b < c, for which a^2 + b^b = c^2. We are given the sum of Pythagorean triplet which is "number" in my case and we have to find the maximum product of a, b and c. I am giving input 5040 as it is the sum of 1260,1680 and 2100. These three numbers forms a Pythagorean triplet. My program should give 4445280000 output as it is the product of the numbers, but it is giving 150312704. Here is my code. I have watched the variables values of a b and c which are correct but the program is not printing the right product of it. 

int noofcases = int.Parse(Console.ReadLine());
for (int i = 0; i < noofcases; i++)
{
    int number = int.Parse(Console.ReadLine());
    long result = -1;
    int a, b, c;
    for( a = 1; a <= number/3; a++)
    {
        b = (((number * number) - (2 * a * number)) / ((2 * number) - (2 * a)));
        c = number - a - b;
        if((a*a) + (b*b) == (c*c))
        {
            result = (a * b * c);
        }
    }
    Console.WriteLine(result);
}

Upvotes: 0

Views: 70

Answers (1)

Martin
Martin

Reputation: 16423

An int in C# is a 32-bit signed integer, which has a range between -2,147,483,648 and 2,147,483,647.

This means that the maximum value that can be stored in an int is 2,147,483,647. Your expected value, 4,445,280,000, is more than twice that maximum value.

When your int value exceeds the maximum of 2,147,483,647, it will roll over to -2,147,483,648 and then count back to 0.

Therefore, 4,445,280,000 will become 150,312,704 as you are experiencing.

Using a long for your result only will not work, because the output of any int multiplied by an int will always be an int unless you use explicit casting.

Simply switch your ints to longs in your program and it will operate as you expect:

int noofcases = int.Parse(Console.ReadLine());
for (int i = 0; i < noofcases; i++)
{
    long number = int.Parse(Console.ReadLine());
    long result = -1;
    long a, b, c;
    for (a = 1; a <= number / 3; a++)
    {
        b = (((number * number) - (2 * a * number)) / ((2 * number) - (2 * a)));
        c = number - a - b;
        if ((a * a) + (b * b) == (c * c))
        {
            result = (a * b * c);
        }
    }
    Console.WriteLine(result);
}

Output:

1
5040
4445280000

Upvotes: 1

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