返回第一个最长的字符串，该字符串由c＃数组中获取的n个连续的字符串组成

Question

我在面试中遇到了这个问题：

我有一个字符串数组和一个整数k。我的任务是返回由数组中的k个连续字符串组成的第一个最长的字符串。

规则：n是字符串数组的长度，如果n = 0或k> n或k <= 0，则返回“”。

示例：

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

输出应为“ abigailtheta”

下面是我尝试过的代码。

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中缺少删除重复项的.Distinct()呼叫。

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，您将获得预期的输出：

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

但是您仍然缺少IF个案例，无法完成所描述的规则：

  

如果n = 0或k> n或k <= 0返回“”

---

更新

正如弗拉基米尔·帕维尔卡（Vladimir Pavelka）在评论中指出的那样，您只需要一种方法来存储单词顺序的初始索引。您可以使用Dictionary来完成此操作：

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;
}

Answer 2

与Smartis讨论后：

public static String LongestConsec(string[] strarr, int k) =>
    String.Join("", 
        strarr.Distinct() // note: this won't change order
              .Select((s, idx) => (s, idx)) // store initial index
              .OrderByDescending(x => x.s.Length) // longest words first
              .Take(k)
              .OrderBy(x => x.idx) // restore original order
              .Select(x => x.s));