已知斐波那契数列第1、2项为1，后续每项均为前两项之和，现有两种C++实现代码如下：

int fiboA(int N)
{
    if (N == 1 || N == 2)
        return 1;
    return fiboA(N - 1) + fiboA(N - 2);
}
int fiboB(int N)
{
    if (N == 1 || N == 2)
        return 1;
    int last2 = 1, last1 = 1;
    int nowVal = 0;
    for (int i = 2; i < N; i++)
    {
        nowVal = last1 + last2;
        last2 = last1;
        last1 = nowVal;
    }
    return nowVal;
}