//请实现下面的函数，输入参数baseStr是一个（可以更改的）字符串，请将其中所有连续出现的多个空格都替换成一个空格，单一空格需保留。
//请直接使用baseStr的空间，如需开辟新的存储空间，不能超过o(N)（注意是小o，N是字符串的长度）。返回值是替换后的字符串的长度。
//样例代码为C#，但可以使用任何语言。如需使用任何库函数，必须同时给出库函数的实现。
class Program
{
    public static int RemoveMultipleSpaces(char[] baseStr)
    {
        if (baseStr == null)
        {
            throw new ArgumentNullException("baseStr");
        }

        int writeCursor = 0;
        bool isLastCharSpace = false;

        for (int i = 0; i < baseStr.Length; i++)
        {
            char current = baseStr[i];

            if (current == ' ')
            {
                if (!isLastCharSpace)
                {
                    isLastCharSpace = true;
                    baseStr[writeCursor++] = current;
                }
            }
            else
            {
                isLastCharSpace = false;
                baseStr[writeCursor++] = current;
            }
        }

        return writeCursor;
    }
}

//样例测试程序（请自行补充更多的测试案例）
[TestFixture]
public class ScannersTest
{
    [Test]
    public void RemoveOneInnterSpaceBlockTest()
    {
        char[] input = "abc    def".ToCharArray();

        int resultLength = Program.RemoveMultipleSpaces(input);

        Assert.AreEqual(7, resultLength);
        Assert.AreEqual("abc def", new string(input, 0, resultLength));
    }

    [Test]
    public void RemoveTwoInnterSpaceBlocksTest()
    {
        char[] input = "abc    def       ghi".ToCharArray();

        int resultLength = Program.RemoveMultipleSpaces(input);

        Assert.AreEqual(11, resultLength);
        Assert.AreEqual("abc def ghi", new string(input, 0, resultLength));
    }

    [Test]
    public void KeepSingleSpaceTest()
    {
        char[] input = " a b   d e ".ToCharArray();

        int resultLength = Program.RemoveMultipleSpaces(input);

        Assert.AreEqual(9, resultLength);
        Assert.AreEqual(" a b d e ", new string(input, 0, resultLength));
    }

    [Test]
    public void AllSpacesTest()
    {
        char[] input = "             ".ToCharArray();

        int resultLength = Program.RemoveMultipleSpaces(input);

        Assert.AreEqual(1, resultLength);
        Assert.AreEqual(" ", new string(input, 0, resultLength));
    }
}