如何比较两个字符串数组并找到公共字符串数组的索引号并将其应用于第三个字符串数组？

Question

I have three string arrays

string[] stringArray= {"AAA", "BBB", "CCC","DDD", "EEE","FFF","GGG","HHH" };
string[] stringArray1 = { "A", "B", "C","D", "E","F","G","H" };
string[] stringArray2 = { "BBB", "DDD","FFF","HHH" };

How could I compare stringArray2 with stringArray and find the index number stringArray that matches. After finding the index ,I need to apply it to stringArray1 and display the results.

I have tried the following code ,but failed to get the match string

int j=0;
string line = null;
List<string> finalstring = new List<string>();

for (int i = 0; i < stringArray.Count; i++)
{ 
   while(stringArray[i] == stringArray2[j])
   {
      line = stringArray2[i];
      finalstring.Add(line);
      j++;
   }
}

Answer 1

I think you have to try like this:

var result = stringArray1.Where(c => // iterating stringArray1
             stringArray2.Where(x => stringArray.Contains(x)) // filtering stringArray2 elements
                         .Any(y=>y.Contains(c))).ToList(); // collect the final result

A Working example for your reference

Answer 2

int j=0;
string line = null;
List<string> finalstring = new List<string>();
for (int i = 0; i < stringArray.Length; i++)
//for (int i = 0; i < stringArray.Count; i++)   // <-- Count is not proper way to get total elements in an array
{
   j = 0;  // <-- you failed to reinitialize 'j' 
   //while(stringArray[i] == stringArray2[j])  // <-- while is not proper way to compare
   if(stringArray[i] == stringArray2[j])
   {
      //line = stringArray2[i];

      //if only first charracter is needed
      finalstring.Add(new string(stringArray2[i][0], 1));

      //if complete string is needed
      //finalstring.Add(stringArray2[i]);

      j++;
   }
}

Above is not an optimized way to do the comparisons. You can try using HashSet class

    string[] stringArray= {"AAA", "BBB", "CCC","DDD", "EEE","FFF","GGG","HHH" };
    string[] stringArray1 = { "A", "B", "C","D", "E","F","G","H" };
    string[] stringArray2 = { "BBB", "DDD","FFF","HHH" };

    //convert string array to hashset
    var hashSet = new HashSet<string>(stringArray);

    int j=0;
    string line = null;
    List<string> finalstring = new List<string>();

    for (int i = 0; i < stringArray2.Length; i++)
    {
        if(hashSet.Contains(stringArray2[i]))
        {
            //if only first charracter is needed
            finalstring.Add(new string(stringArray2[i][0], 1));
        }
    } 

Answer 3

List<string> finalList = new List<string>();
stringArray.Select((value,index) => new { value, index })
.Where(num => stringArray2.Contains(num.value)).ToList()
.ForEach(num => finalList.Add(stringArray1[num.index]));

Answer 4

You are trying to compare the elements on same index but you have to search the element of stringArray2 in stringArray . You can use Array.IndexOf to find in Array the required element.

string[] stringArray= {"AAA", "BBB", "CCC","DDD", "EEE","FFF","GGG","HHH" };
string[] stringArray1 = { "A", "B", "C","D", "E","F","G","H" };
string[] stringArray2 = { "BBB", "DDD","FFF","HHH" };
    int j=0;
string line = null;
List<string> finalstring = new List<string>();

for (int i = 0; i < stringArray2.Count(); i++)
{ 
   if(Array.IndexOf(stringArray, stringArray2[i]) != -1)
   {
      int idx = Array.IndexOf(stringArray1, stringArray2[i][0].ToString());
      if(idx!=-1)
        finalstring.Add(stringArray1[idx]);
    }  
}

Edit using Linq

var result2 = stringArray1.Where(c=>
              stringArray2.Intersect(stringArray)
              .Any(i=>i.Contains(c)));

Answer 5

you could do it with selecting the index via Linq ( where >= 0 filters out all non matches):

string[] stringArray = { "AAA", "BBB", "CCC", "DDD", "EEE", "FFF", "GGG", "HHH" };
string[] stringArray1 = { "A", "B", "C", "D", "E", "F", "G", "H" };
string[] stringArray2 = { "BBB", "DDD", "FFF", "HHH" };

var matches = stringArray2
    .Select(s => Array.FindIndex(stringArray, s2 => s2 == s))
    .Where(i => i >= 0).Select(i => stringArray1[i])
    .ToList();

Here a dotnetfiddle