递归二分查找程序

Question

下面是我的递归二进制搜索方法。这是为了从一个排序的列表中找到一个电话号码，但它只对文件中的第一个号码有效，并显示所有其他号码都找不到。有人能帮我找出哪里出了问题吗？

static int binary (String num, String[] phone, int low, int high)
{
    if ((high - low) <= 1)
    {
        if (phone [low].equals (num))
        {
            return low;
        }
        else if (phone [high].equals (num))
        {
            return high;
        }
        else
        {
            return -1;
        }
    }
    int mid = (low + high) / 2;
    if (phone [mid].compareTo (num) > 0)
    {
        return binary (num, phone, 0, mid);
    }
    else if (phone [mid].compareTo (num) < 0)
    {
        return binary (num, phone, mid, high);
    }
    else
    {
        return -1;
    }
}

Answer 1

我觉得你想

if (phone [mid].compareTo (num) > 0)
{
    return binary (num, phone, low, mid-1);
}
else if (phone [mid].compareTo (num) < 0)
{
    return binary (num, phone, mid+1, high);
}

此外，您需要执行比必要的检查更多的检查：

static int binary (String num, String[] phone, int low, int high)
{
    if(low > high)
    {
        return -1;
    }
    int mid = (low + high) / 2;
    int compare = phone[mid].compareTo(num);
    return compare > 0 ? binary (num, phone, low, mid-1);
        : compare < 0 ? binary (num, phone, mid+1, high);
        -1;
}