Self-hatred

Project Euler Problem #12

This was a question of two parts:

1. Calculate the next triangle number in sequence.
2. Take said triangle number and calculate how many divisors it has. Loop until you find one with 500, and break.

The first part was simple:

Start with n = 1. For every iteration of the loop, add n to n, and add 1:

n = 1
n = n + n + 1

The second part…not so simple. I’ll honestly say I am struggling with understanding the correct way to test for divisors; this works, however:

Take a number, i. Find the square root of i. Loop. Check every integer up to n to see if it divides evenly. Increment the count. Double the answer and return it.

using System;

public class Twelve
{
	static void Main()
	{
		long a = 1;
		long b = 1;
		long c = 0;

		while (c < = 500)
		{
			c = factors(a);

			if (c > 500)
			{
				Console.Write("\n{0}\n", b);
				break;
			}
			else
			{
				a += b + 1;
				b++;
			}
		}
	}

	static long factors(long a)
	{
		long b = 1;

		for (int i = 1; i < = Math.Sqrt(a); i++)
			if (a % i == 0)
				b++;

		return 2 * b;
	}
}

Tagged with: c, code, csharp, mathematics, programming, project euler, projecteuler, triangle numbers

Categorised as: programming