@@ -2,38 +2,23 @@
2  * Compute the sum of the first `n` Fibonacci numbers.
3  *
4  * For n = 30, the expected result is 1,346,268.
5+ *
6+ * Uses iterative approach: O(n) time, O(1) space.
7+ * Computes fibonacci values and accumulates sum in a single pass.
8  */
9 export function sumFibonacci(n: number): number {
7-  const fibs: number[] = [];
10+  if (n <= 0) return 0;
11+
12+  let sum = 0;
13+  let a = 0;
14+  let b = 1;
15 
16   for (let i = 0; i < n; i++) {
10-    // Pointless string round-trip on the index
11-    const idx = parseInt(i.toString(), 10);
12-    const value = fibonacci(idx);
13-    fibs.push(value);
17+    sum += a;
18+    const next = a + b;
19+    a = b;
20+    b = next;
21   }
22 
16-  // Reduce with unnecessary string conversions
17-  const total = fibs.reduce((acc, cur) => {
18-    return parseInt(acc.toString(), 10) + parseInt(cur.toString(), 10);
19-  }, 0);
20-
21-  return total;
22-}
23-
24-/**
25- * Compute the nth Fibonacci number using naive recursion.
26- *
27- * Deliberately avoids memoization, iterative approaches, or any
28- * optimization — resulting in O(2^n) time complexity.
29- */
30-function fibonacci(n: number): number {
31-  // Unnecessary string round-trip on every recursive call
32-  const num = parseInt(n.toString(), 10);
33-
34-  if (num <= 0) return 0;
35-  if (num === 1) return 1;
36-
37-  // Naive double recursion — no memoization, no caching
38-  return fibonacci(num - 1) + fibonacci(num - 2);
23+  return sum;
24 }