C# count ocurrences of several char in string using regex.Matches.count once

Question

Having a string like:

0x1TTTT10TT1Tx01Tx1001xxx100T0TxT1T1TxTxTxx0TT0000000x0xTxT1Tx0T0x10x1

I want to get:

 0 appears 20
 1 appears 12 
 x appears 17
 T appears 21

If I use

        int zero = Regex.Matches(input, "0").Count;
        int one  = Regex.Matches(input, "1").Count;
        int x    = Regex.Matches(input, "x").Count;
        int T    = Regex.Matches(input, "T").Count;

How to accomplish same result using more efficient approach using Regex?

Why did you put "efficient" and "regex" in the same sentence? :) — Blue Ice
– Blue Ice, Commented Nov 18, 2013 at 23:57
Yes you are right, I should have written, try to make more efficient regex code? — edgarmtze
– edgarmtze, Commented Nov 18, 2013 at 23:58
Well, you could use built-in string searching libraries depending on which programming language you are using. — Blue Ice
– Blue Ice, Commented Nov 19, 2013 at 0:02
I am using c#, maybe doing a for loop with case statements will be enough — edgarmtze
– edgarmtze, Commented Nov 19, 2013 at 0:02
Try looking here: stackoverflow.com/questions/10391481/… and here: stackoverflow.com/questions/541954/… — Blue Ice
– Blue Ice, Commented Nov 19, 2013 at 0:04

Lukazoid · Accepted Answer · 2013-11-19 00:08:09Z

1

This is not really the real purpose of Regular Expressions. I would instead advise the use of a loop over the characters, like the following:

int zeroCount = 0;
int oneCount = 0;
int xCount = 0;
int tCount = 0;
foreach(var ch in input)
{
    switch(ch)
    {
        case '0':
            zeroCount++;
            break;
        case '1':
            oneCount++;
            break;
        case 'x':
            xCount++;
            break;
        case 'T':
            tCount++;
            break;
    }
}

Unfortunately the most efficient isn't usually the most concise.

answered Nov 19, 2013 at 0:08

Lukazoid

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