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Four Millionacci – Project Euler #2

Problem 2

Each new term in the Fibonacci sequence is generated by adding the previous two terms. By starting with 1 and 2, the first 10 terms will be:

1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ...

Find the sum of all the even-valued terms in the sequence which do not exceed four million.

Code:

using System;

namespace Problem_2
{
    class Entry
    {
        static void Main(string[] args)
        {
            int limit = 4000000;
            int a = 1;
            int b = 2;
            int c = 0;
            int sum = 0;
            while (b < limit)
            {
                c = a + b;
                a = b;
                b = c;
                if (a % 2 == 0)
                    sum += a;
            }
            Console.WriteLine(sum);
            Console.ReadLine();
        }
    }
}

Answer:
4613732

FizzBuzz Plus – Project Euler #1

Problem 1

If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23.

Find the sum of all the multiples of 3 or 5 below 1000.

Code:

using System;

namespace Problem_1
{
    class Entry
    {
        static void Main(string[] args)
        {
            Int32 sum = 0;
            //Sum all multiples of 3 below 1000
            for (int i = 3; i < 1000; i += 3)
            {
                sum += i;
            }
            //Add all multiples of 5 below 1000 to that
            for (int j = 5; j < 1000; j += 5)
            {
                //Don't count multiples of both twice
                if (j % 3 != 0)
                    sum += j;
            }
            System.Console.WriteLine(sum.ToString());
            System.Console.ReadLine();
        }
    }
}

Answer:
233168