How to check if string contains single occurence of substring?

Question

I have this:

string strings = "a b c d d e";

And I need something similar to string.Contains(), but I need to know not only whether a string is present(in case above a letter), but also if it is present only ONE SINGLE time.

How can I achieve this?

why not use a simple Linq statement to return the character that occurs the most you can use a `GroupBy` and `OrderDescending` — MethodMan, Feb 08 '13 at 15:12
possible duplicate of [Find the most occurrence of a character in string C#?](http://stackoverflow.com/questions/5069687/find-the-most-occurrence-of-a-character-in-string-c) — MethodMan, Feb 08 '13 at 15:13

Ivaylo Strandjev · Accepted Answer · 2013-02-08T15:53:15.833

17

You can use LastIndexOf(String) and IndexOf(String) and verify that the values returned are equal. Of course also check if the String is found at all(i.e the returned value is not -1).

edited Feb 08 '13 at 15:53

answered Feb 08 '13 at 15:04

Ivaylo Strandjev

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1

Actually, the latter is just `IndexOf(String)`, no "First". – Jeppe Stig Nielsen Feb 08 '13 at 15:52

score 7 · Answer 2 · answered Feb 08 '13 at 15:04

7

You could use LINQ

int count = strings.Count(f => f == 'd');

answered Feb 08 '13 at 15:04

Andrew Beal

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-1 Andrew this is good but the condition should not be hard coded – MethodMan Feb 08 '13 at 15:05
3

This only works for characters though. He mentioned he wanted to find an entire string within the original string. – jamesmillerio Feb 08 '13 at 15:05
Bit Destroyer - True, I missed that – Andrew Beal Feb 08 '13 at 15:06

score 1 · Answer 3 · answered Feb 08 '13 at 15:10

1

An alternative

if(Regex.Matches(input,Regex.Escape(pattern)).Count==1)

answered Feb 08 '13 at 15:10

Anirudha

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score 1 · Answer 4 · answered Jan 19 '18 at 08:26

1

Another simple alternative:

if(strings.Split(new [] { "a" }, StringSplitOptions.None).Length == 2)

answered Jan 19 '18 at 08:26

Felix Keil

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Pandian · Answer 5 · 2013-02-08T16:17:16.523

0

try like below... it will help you...

string strings = "a b c d d e";
string text ="a";
int count = 0;
int i = 0;
while ((i = strings.IndexOf(text, i)) != -1)
{
    i += text.Length;
    count++;
}
if(count == 0)
Console.WriteLine("String not Present");

if(count == 1)
Console.WriteLine("String Occured Only one time");

if(Count>1)
Console.WriteLine("String Occurance : " + count.Tostring());

edited Feb 08 '13 at 16:17

answered Feb 08 '13 at 15:21

Pandian

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You seem to confuse your `strings` and `text` variables. For example when you say `text.IndexOf(text, i)`. Note that it might be interesting to know if the search string existed as two substrings which overlapped. Like if we searched for substring `"reassure"` inside `"XXXXXreassureassureXX"`, one could want to count two matches (not clear in the question). So watch how much you increment `i`. Also watch the increment of `i` because if you get out of the bounds of the `strings` variable, the next `IndexOf` will throw an exception, not just return `-1`. – Jeppe Stig Nielsen Feb 08 '13 at 16:12
First try your own code with `strings = "a b c d d e"` and `text = "e"`. After you fixed that problem, try you code with `strings = "XXXXXreassureassureXX"` and `text = "reassure"`. What answer do you prefer in that case? – Jeppe Stig Nielsen Feb 08 '13 at 16:38

score 0 · Answer 6 · answered Feb 08 '13 at 16:22

    string source = "a b c d d e";
    string search = "d";
    int i = source.IndexOf(search, 0);
    int j = source.IndexOf(search, i + search.Length);
    if (i == -1)
        Console.WriteLine("No match");
    else if (j == -1)
        Console.WriteLine("One match");   
    else
        Console.WriteLine("More match");

How to check if string contains single occurence of substring?

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