Replace some letters of string with specific symbol

Question

i have a string like this:

string word="HELLO";

and clear indexes of string like this:

IList<string> clearIndexes = indexes;// for example {2,4}

what i want is

 *E*L*// the 2th and 4th elements are clear and the other should be shown with *,

how can I do that?

Why is `clearIndexes` a `List` and not a `List`? – Tim Schmelter Apr 04 '16 at 14:51 — Tim Schmelter, Apr 04 '16 at 14:51

fubo · Accepted Answer · 2016-04-04T14:48:02.690

5

here is one approach with the required List<string> of indexes

string word = "HELLO";
List<string> clearIndexes = new List<string> { "2", "4" };
string result = new string(word.Select((c, i) => !clearIndexes.Contains((i+1).ToString()) ? '*' : c).ToArray());

usually a index starts at 0 so i added (i+1) to get the result *E*L*

edited Apr 04 '16 at 14:48

answered Apr 04 '16 at 14:34

fubo

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thanx for your response but clearIndexes are list of strings and I cant change the type of it, so I get error. – someone Apr 04 '16 at 14:41
@someone, why is it `List` and why position of character to leave un-starred is not index (but `index + 1`) ? – Sinatr Apr 04 '16 at 14:42
Slightly better would be `new string(word.Select((c, i) => !clearIndexes.Contains(i+1) ? '*' : c).ToArray());` to avoid converting each `char` to a `string`. – juharr Apr 04 '16 at 14:44
@Sinatr these indexes are manipulated with a linq query of this: data.Where(s => s.StartsWith(Word)).Where(s => !s.EndsWith("X")).Select(s=>s.Remove(0,Word.Length)) and the result is list of strings – someone Apr 04 '16 at 14:45

score 0 · Answer 2 · answered Apr 04 '16 at 14:47

You can use the following code-snippet:

string word = "HELLO";
string[] strIndexes = new string[] { "2", "4" };
//
int[] replacementPositions = Enumerable.Range(1, word.Length) // nonzero-based
    .Where(i => Array.IndexOf(strIndexes, i.ToString()) == -1)
    .ToArray();
StringBuilder sb = new StringBuilder(word);
for(int i = 0; i < replacementPositions.Length; i++)
    sb[replacementPositions[i] - 1] = '*';

string result = sb.ToString();

score 0 · Answer 3 · answered Apr 04 '16 at 15:11

You could also use a simple for-loop and manipulate the char[] returned by ToCharArray:

char[] chars = word.ToCharArray();
for (int i = 0; i < chars.Length; i++)
    chars[i] = clearIndexes.Contains((i+1).ToString()) ? chars[i] : '*';
word = new string(chars);

In general it would be better to use a List<int> and to store the index which is zero based.

Replace some letters of string with specific symbol

3 Answers3