package ProjectEuler;

/**
 * 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:
 *
 * <p>1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ...
 *
 * <p>By considering the terms in the Fibonacci sequence whose values do not exceed four million,
 * find the sum of the even-valued terms.
 *
 * <p>Link: https://projecteuler.net/problem=2
 */
public class Problem02 {
  public static void main(String[] args) {
    int[][] testNumbers = {
      {10, 10}, /* 2 + 8 == 10 */
      {15, 10}, /* 2 + 8 == 10 */
      {2, 2},
      {1, 0},
      {89, 44} /* 2 + 8 + 34 == 44 */
    };

    for (int[] ints : testNumbers) {
      assert solution1(ints[0]) == ints[1];
    }
  }

  private static int solution1(int n) {
    int sum = 0;
    int first = 1;
    int second = 2;
    while (second <= n) {
      if (second % 2 == 0) {
        sum += second;
      }
      int temp = first + second;
      first = second;
      second = temp;
    }
    return sum;
  }
}