public static int RemoveDuplicates(ref int[] array)
{
    int size = array.Length;

    // if 0 or 1, return 0 or 1:
    if (size  < 2) {
        return size;
    }

    int current = 0;
    for (int candidate = 1; candidate < size; ++candidate) {
        if (array[current] != array[candidate]) {
            array[++current] = array[candidate];
        }
    }

    // index to count conversion:
    return ++current;
}

使用Distinct和stringcompararer删除重复和忽略区分大小写。InvariantCultureIgnoreCase

string[] array = new string[] { "A", "a", "b", "B", "a", "C", "c", "C", "A", "1" };
var r = array.Distinct(StringComparer.InvariantCultureIgnoreCase).ToList();
Console.WriteLine(r.Count); // return 4 items

这里有一个O(n*n)方法，它使用O(1)空间。

void removeDuplicates(char* strIn)
{
    int numDups = 0, prevIndex = 0;
    if(NULL != strIn && *strIn != '\0')
    {
        int len = strlen(strIn);
        for(int i = 0; i < len; i++)
        {
            bool foundDup = false;
            for(int j = 0; j < i; j++)
            {
                if(strIn[j] == strIn[i])
                {
                    foundDup = true;
                    numDups++;
                    break;
                }
            }

            if(foundDup == false)
            {
                strIn[prevIndex] = strIn[i];
                prevIndex++;
            }
        }

        strIn[len-numDups] = '\0';
    }
}

上面的哈希/linq方法是你在现实生活中通常会使用的方法。然而，在面试中，他们通常想要设置一些限制，例如常量空间，这就排除了哈希或没有内部api——这就排除了使用LINQ。

这可能取决于你有多想设计解决方案-如果数组永远不会那么大，你不关心排序列表，你可能想尝试类似于下面的东西:

    public string[] RemoveDuplicates(string[] myList) {
        System.Collections.ArrayList newList = new System.Collections.ArrayList();

        foreach (string str in myList)
            if (!newList.Contains(str))
                newList.Add(str);
        return (string[])newList.ToArray(typeof(string));
    }

下面经过测试和工作的代码将从数组中删除重复项。你必须包括系统。集合名称空间。

string[] sArray = {"a", "b", "b", "c", "c", "d", "e", "f", "f"};
var sList = new ArrayList();

for (int i = 0; i < sArray.Length; i++) {
    if (sList.Contains(sArray[i]) == false) {
        sList.Add(sArray[i]);
    }
}

var sNew = sList.ToArray();

for (int i = 0; i < sNew.Length; i++) {
    Console.Write(sNew[i]);
}

如果你愿意，你可以把它打包成一个函数。

在下面找到答案。

class Program
{
    static void Main(string[] args)
    {
        var nums = new int[] { 1, 4, 3, 3, 3, 5, 5, 7, 7, 7, 7, 9, 9, 9 };
        var result = removeDuplicates(nums);
        foreach (var item in result)
        {
            Console.WriteLine(item);
        }
    }
    static int[] removeDuplicates(int[] nums)
    {
        nums = nums.ToList().OrderBy(c => c).ToArray();
        int j = 1;
        int i = 0;
        int stop = 0;
        while (j < nums.Length)
        {
            if (nums[i] != nums[j])
            {
                nums[i + 1] = nums[j];
                stop = i + 2;
                i++;
            }
            j++;
        }
        nums = nums.Take(stop).ToArray();
        return nums;
    }
}

这是基于我刚刚解决的一个测试的一点贡献，可能对这里其他顶级贡献者的改进有所帮助。 以下是我所做的事情:

I used OrderBy which allows me order or sort the items from smallest to the highest using LINQ I then convert it to back to an array and then re-assign it back to the primary datasource So i then initialize j which is my right hand side of the array to be 1 and i which is my left hand side of the array to be 0, i also initialize where i would i to stop to be 0. I used a while loop to increment through the array by going from one position to the other left to right, for each increment the stop position is the current value of i + 2 which i will use later to truncate the duplicates from the array. I then increment by moving from left to right from the if statement and from right to right outside of the if statement until i iterate through the entire values of the array. I then pick from the first element to the stop position which becomes the last i index plus 2. that way i am able to remove all the duplicate items from the int array. which is then reassigned.