feat: bunch of algos

src/project-euler/problem-0002/main.ts

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+/**
+ * @copyright NHCarrigan
+ * @license Naomi's Public License
+ * @author Naomi Carrigan
+ */
+
+/**
+ * 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, ...
+ * By considering the terms in the Fibonacci sequence whose values do not exceed four million, find the sum of the even-valued terms.
+ * @param limit - The limit to find the Fibonacci sequence below.
+ * @returns The sum of the even-valued terms in the Fibonacci sequence below the limit.
+ * @see https://www.freecodecamp.org/learn/project-euler/project-euler-problems-1-to-100/problem-2-even-fibonacci-numbers
+ */
+export const fiboEvenSum = (limit: number): number => {
+  let current = 3,
+    previous = 2,
+    sum = 2;
+
+  while (current <= limit) {
+    if (current % 2 === 0) {
+      sum = sum + current;
+    }
+    const next = current + previous;
+    previous = current;
+    current = next;
+  }
+  return sum;
+};