c# - 返回c#中数组中取n个连续字符串组成的第一个最长的字符串

Question

我在面试中遇到了这个问题:

我得到了一个字符串数组 strarr 和一个整数 k。我的任务是返回数组中取的k个连续字符串组成的第一个最长的字符串。

规则:n为字符串数组的长度，若n=0或k>n或k<=0则返回""。

示例:

LongestConsec(["zone", "abigail", "theta", "form", "libe", "zas", "theta", "abigail"], 2) 

输出应该是“abi​​gailtheta”

下面是我试过的代码..它不工作。

public class LongestConsecutives
{
    public static String LongestConsec(string[] strarr, int k)
    {
        string final = String.Join("", strarr.OrderByDescending(s=>s.Length).Take(k)); 
        return final;
    }

    public static void Main()
    {
        string s1 = LongestConsec(new String[] { "wlwsasphmxx", "owiaxujylentrklctozmymu", "wpgozvxxiu" }, 2); //op="wlwsasphmxxowiaxujylentrklctozmymu"
        string s2 = LongestConsec(new string[] { "itvayloxrp", "wkppqsztdkmvcuwvereiupccauycnjutlv", "vweqilsfytihvrzlaodfixoyxvyuyvgpck" }, 2);//op="wkppqsztdkmvcuwvereiupccauycnjutlvvweqilsfytihvrzlaodfixoyxvyuyvgpck"
        string s3 = LongestConsec(new String[] { "zone", "abigail", "theta", "form", "libe", "zas" }, -2);//op=""
        string s4 = LongestConsec(new String[] { "it", "wkppv", "ixoyx", "3452", "zzzzzzzzzzzz" }, 3);//op="ixoyx3452zzzzzzzzzzzz"
        string s5 = LongestConsec(new String[] { "it", "wkppv", "ixoyx", "3452", "zzzzzzzzzzzz" }, 15);//op=""
        string s6 = LongestConsec(new String[] { "it", "wkppv", "ixoyx", "3452", "zzzzzzzzzzzz" }, 0);//op=""
        string s7 = LongestConsec(new String[] { }, 3);//op=""
        string s8 = LongestConsec(new String[] { "zone", "abigail", "theta", "form", "libe", "zas", "theta", "abigail" }, 2);//op="abigailtheta"
        string s9 = LongestConsec(new String[] { "ejjjjmmtthh", "zxxuueeg", "aanlljrrrxx", "dqqqaaabbb", "oocccffuucccjjjkkkjyyyeehh" }, 1);//op="oocccffuucccjjjkkkjyyyeehh"
    }
}

Answer 1

您在 LINQ 中缺少用于删除重复项的 .Distinct() 调用。

public static String LongestConsec(string[] strarr, int k)
{
    string final = String.Join("", 
        strarr.Distinct()                       // Remove Duplicates
              .OrderByDescending(s => s.Length) // Order by Length
              .Take(k)                          // Take from List
    );

    return final;
} 

修改后，您将得到预期的输出:

string target = LongestConsec(new string[] { "zone", "abigail", "theta", "form", "libe", "zas", "theta", "abigail"}, 2);
// target = "abigailtheta"

但是您仍然缺少完成您描述的规则的 IF 案例:

if n = 0 or k > n or k <= 0 return ""

---

更新

正如 Vladimir Pavelka 在评论中指出的那样，您只需要一种方法来存储词序的初始索引。你可以用像这样的 Dictionary 来做到这一点:

public static String LongestConsec(string[] strarr, int k)
{
    var dict = new Dictionary<string, int>();
    for (int i = 0; i < strarr.Length; i++)
    {
        if (!dict.ContainsKey(strarr[i]))  // Preventing duplicates
        {
            dict.Add(strarr[i], i + 1);
        }
    }

    string final = String.Join("",
        dict.OrderByDescending(s => s.Key.Length)
            .Take(k)
            .OrderBy(s => s.Value)
            .Select(s => s.Key)
    );

    return final;
}