有序数组

int GetNumberSameAdIndex(vector<int>number)
{
    if (number.size() == 0)return -1;
    int L = 0, R = number.size() - 1;
    while (L <= R)
    {
        int middle = (R - L) / 2 + L;
        if (number[middle] == middle)return middle;
        if (number[middle] > middle)R = middle - 1;
        else L = middle + 1;//如果等于前面已经跳出了
    }
    if (L == number.size()-1)return L;
    return -1;
}