二进制搜索数组以显示包含字符串字段的行

Question

我有一个按钮，它应该接受 'surname' 字符串输入，在目录数组中搜索与该姓氏相关的 'record' 结构，并将该记录输出到列表视图。该目录由多行 3 个字符串记录结构组成：姓氏、名字、分机号。

经过数天搜索类似的 SO 问题和其他来源，我拼凑了似乎最适合我的问题的方法，但出于某种原因，我的主要搜索方法并没有引用我的辅助方法。你能告诉我你为什么这么认为吗？如果我设法使参考有效，你认为它是否有效？如果不行，还有其他建议吗？

仅供参考，我的 if 语句有点不守规矩，因为我的项目要求姓氏不区分大小写并接受部分字符串匹配。

private void SearchSurname()
    {
        Array.Sort(directory, (x, y) => String.Compare(x.surname, y.surname));

        ClearForm();
        int surnameIndex = Array.BinarySearch(directory, txtSurname.Text);

        if (directory[surnameIndex].surname.ToUpper().Substring(0, txtSurname.Text.Length).Contains(txtSurname.Text.ToUpper()))
        {
            ListViewItem record = new ListViewItem();

            // Send each field in current record to single listview item
            record.Text = (Convert.ToString(txtSurname.Text));
            record.SubItems.Add(Convert.ToString(txtForename.Text));
            record.SubItems.Add(Convert.ToString(txtExtCode.Text));

            // Display new record listview item in listview
            lvDirectory.Items.Add(record);
        }
    }

    public int BinarySearch(string[] directory, string searchTerm)
    {
        int first = 0;
        int last = directory.Length - 1;
        int position = -1;
        bool found = false;
        int compCount = 0;
        searchTerm = txtSurname.Text;

        while (found != true && first <= last)
        {
            int middle = (first + last) / 2;

            if (string.Compare(directory[middle], searchTerm, true) == 0)
            {
                found = true;
                position = middle;
                compCount++;
            }
            else if (string.Compare(directory[middle], searchTerm, true) > 0)
            {
                last = middle;
                compCount++;
            }
            else
            {
                first = middle;
                compCount++;
            }
        }
        return position;
    }

编辑：根据 Olivier Jacot-Descombes 的回答更新了代码：

private void SearchSurname()
    {
        // Sort directory alphabetically by surname
        Array.Sort(directory, (x, y) => String.Compare(x.surname, y.surname));

        ClearForm();

        // In directory, find line index of search term
        int surnameIndex = BinarySearch(directory, txtSurname.Text);

        ListViewItem record = new ListViewItem();

        // Send each field in current record to single listview item
        record.Text = (Convert.ToString(directory[surnameIndex].surname));
        record.SubItems.Add(Convert.ToString(directory[surnameIndex].forename));
        record.SubItems.Add(Convert.ToString(directory[surnameIndex].extCode));

        // Display new record listview item in listview
        lvDirectory.Items.Add(record);
    }

    private int BinarySearch(record[] directory, string searchTerm)
    {
        int first = 0;
        int last = directory.Length - 1;
        int surnameIndex = -1;
        bool indexFound = false;

        // While index not found and there are still points in the array to check
        while (indexFound != true && first < last)
        {
            int middle = (first + last) / 2;

            // If surname field in middle record of directory array matches the search term
            if (string.Compare(directory[middle].surname, searchTerm, true) == 0)
            {
                // Index found!
                indexFound = true;
                surnameIndex = middle;
                MessageBox.Show("If 1");
            }
            // If surname field in middle record of directory array is higher, alphabetically, than the search term
            else if(string.Compare(directory[middle].surname, searchTerm, true) > 0)
            {
                // The next search will be between the first and the current middle records of the array
                last = middle;
                MessageBox.Show("If 2");
            }
            // If surname field in middle record of directory array is lower, alphabetically, than the search term
            else
            {
                // The next search will be between the current middle and the highest records of the array
                first = middle;
                MessageBox.Show("If 3");
            }
        }
        return surnameIndex;
    }

Answer 1

您的 SearchSurname 方法调用 Array.BinarySearch，这是 Array Class 的静态方法。如果你想调用你自己的方法，你必须这样写：

int surnameIndex = BinarySearch(directory, txtSurname.Text); // Without "Array."

您正在使用不区分大小写的比较，因为 String.Compare 的第三个参数是 true。

你可以使用

if (string.StartsWith(directory[middle], searchTerm,
                      StringComparison.CurrentCultureIgnoreCase))

只搜索名字的开头。但是如果几个名字匹配就会有问题。例如。您正在搜索 "smit" 并且数组中有 "Smith" 和 "Smithy"。因此，您必须测试找到的匹配项之前和之后的条目，并且 return 所有匹配项作为可能的结果。

二进制搜索数组以显示包含字符串字段的行

Binary searching array to display row containing string field

c#

arrays

string

binary-search