用AI帮我写程序

# AI生成的Python代码示例（优化前）
def calculate_fibonacci(n):
    if n <= 1:
        return n
    else:
        return calculate_fibonacci(n-1) + calculate_fibonacci(n-2)

# 小发猫优化后的代码示例（优化后）
def fibonacci_sequence(position):
    if position < 2:
        return position
    
    prev, current = 0, 1
    for _ in range(2, position + 1):
        prev, current = current, prev + current
    
    return current