I want to check if a string contains more than one character in the string? If i have a string 12121.23.2 so i want to check if it contains more than one . in the string.
You can compare IndexOf
to LastIndexOf
to check if there is more than one specific character in a string
without explicit counting:
var s = "12121.23.2";
var ch = '.';
if (s.IndexOf(ch) != s.LastIndexOf(ch)) {
...
}
You can easily count the number of occurences of a character with LINQ:
string foo = "12121.23.2";
foo.Count(c => c == '.');
If performance matters, write it yourself:
public static bool ContainsDuplicateCharacter(this string s, char c)
{
bool seenFirst = false;
for (int i = 0; i < s.Length; i++)
{
if (s[i] != c)
continue;
if (seenFirst)
return true;
seenFirst = true;
}
return false;
}
In this way, you only make one pass through the string's contents, and you bail out as early as possible. In the worst case you visit all characters only once. In @dasblinkenlight's answer, you would visit all characters twice, and in @mensi's answer, you have to count all instances, even though once you have two you can stop the calculation. Further, using the Count
extension method involves using an Enumerable<char>
which will run more slowly than directly accessing the characters at specific indices.
Then you may write:
string s = "12121.23.2";
Debug.Assert(s.ContainsDuplicateCharacter('.'));
Debug.Assert(s.ContainsDuplicateCharacter('1'));
Debug.Assert(s.ContainsDuplicateCharacter('2'));
Debug.Assert(!s.ContainsDuplicateCharacter('3'));
Debug.Assert(!s.ContainsDuplicateCharacter('Z'));
I also think it's nicer to have a function that explains exactly what you're trying to achieve. You could wrap any of the other answers in such a function too, however.
Boolean MoreThanOne(String str, Char c)
{
return str.Count(x => x==c) > 1;
}
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