Given the following strings = new string[] { "a", "a", "a", "b", "b", "c", "c", "c", "c", "d" };
How would you replace the duplicate items to produce the following output: { "a", "Duplicate", "Duplicate", "b", "Duplicate", "c", "Duplicate", "Duplicate", "Duplicate", "d" }
For something like this, particularly if you intend to modify the array and not produce a new sequence, I would prefer an old fashioned loop. It would seem to me to be more obvious, less "clever," and easier to understand. If you are of a similar opinion, the loop is fairly easy to write. Create a set that will hold distinct items, and replace items that have already been added to the set.
var set = new HashSet<string>();
for (int i = 0; i < strings.Length; i++)
{
if (set.Contains(strings[i]))
{
strings[i] = "Duplicate";
}
else
{
set.Add(strings[i]);
}
}
Given your input, your output would be:
a
Duplicate
Duplicate
b
Duplicate
c
Duplicate
Duplicate
Duplicate
d
if (!set.Add(strings[i])) strings[i] = "Duplicate";
Using Linq, you could do this.
s = s.GroupBy(x=>x)
.SelectMany(x=>x.Take(1) // Take first element
.Concat(x.Skip(1).Select(r=>"Duplicate")) // Replace other elements with 'Duplicate'
)
.ToArray();
Check Working example
In case you are searching for a method which will mark only consecutive duplicates:
var strings = new string[] { "a", "a", "a", "b", "b", "c", "c", "c", "c", "d" };
var output = new string[strings.Length];
output[0] = strings[0];
for(int i = 1; i < strings.Length; i++)
{
output[i] = strings[i] != strings[i - 1] ? strings[i] : "duplicate";
}
only consecutive duplicates.Try This
strings = new string[] { "a", "a", "a", "b", "b", "c", "c", "c", "c", "d" };
var myArray = new System.Collections.ArrayList();
foreach(var item in strings){
if (!myArray.Contains(item))
myArray.Add(item);
else
myArray.Add('Duplicate');
}
ArrayList is not a preferred collection to use in modern C#, there are better choices. Secondly, this solution will become increasingly slow as the size of strings grows, it will not scale well.Just a thought on writing a lambda expression for this
var output = strings.ToList().Select((x, y) => Array.IndexOf(strings, x) == y ? x : "Duplicate");
