Solution 2

src/bin/problem_2.rs

@@ -0,0 +1,29 @@
+fn main() {
+    let result = fibonacci_even_sum(4_000_000);
+    println!("Result: {}", result);
+}
+
+fn fibonacci_even_sum(limit: i64) -> i64 {
+    let mut previous = (1, 2);
+    let mut sum = 2;
+    while previous.0 + previous.1 < limit {
+        previous = (previous.1, previous.0 + previous.1);
+
+        if previous.1 % 2 == 0 {
+            sum += previous.1;
+        }
+    }
+
+    return sum;
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::fibonacci_even_sum;
+
+    #[test]
+    fn it_works() {
+        let result = fibonacci_even_sum(100);
+        assert_eq!(result, 44);
+    }
+}