Multiple replace

Question

Have:

"a__b_c_____d__e_f__"

Need:

"a_b_c_d_e_f_"

ie: Replace all the "___" substrings (1 or more underscores) with "_" (single underscore) without loops.

I really don't know any nice solution. That's why asked. Maybe regexp... — Sergey Metlov, Jul 23 '12 at 20:04
Possible duplicate: [How do I replace multiple spaces with a single space in C#?](http://stackoverflow.com/q/206717/416627) — Dave Rager, Jul 23 '12 at 20:07
nope. look at the accepted answer. the only loops inside the `Regex` implementation — Sergey Metlov, Jul 23 '12 at 20:26
Jeez. Replace one or more _'s in a row with a single _. This is trivial in Regex. Like `_+` trivial. (edit) oh, and look at the answer. — , Jul 24 '12 at 01:35

score 13 · Accepted Answer · answered Jul 23 '12 at 20:04

13

Use a regular expression, e.g.

var input = "a__b_c_____d__e_f__";
var output = Regex.Replace(input, "_+", "_");

answered Jul 23 '12 at 20:04

Brian Rasmussen

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+1, I was about to link to [this answer](http://stackoverflow.com/a/206946/416627) with the same suggested modification. – Dave Rager Jul 23 '12 at 20:06

score 1 · Answer 2 · answered Jul 23 '12 at 20:05

1

You can achieve this by using RegularExpressions as follow

string str = "a__b_c_____d__e_f__";
string newStr = System.Text.RegularExpressions.Regex.Replace(str, "_{2,}", "_");

answered Jul 23 '12 at 20:05

Pierluc SS

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score 0 · Answer 3 · answered Jul 23 '12 at 20:06

0

 var cleanString = Regex.Replace("a__b_c_____d__e_f__", "(_)+", "$1");

answered Jul 23 '12 at 20:06

Gabe

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Moses · Answer 4 · 2012-07-23T20:09:05.823

-1

This should get you started.

cat file | perl -e "s/\_+/\_/g"

edited Jul 23 '12 at 20:09

answered Jul 23 '12 at 20:03

Moses

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+1 .. because it's same same regular expression and suggests that the poster continues the thinking .. although perhaps should just be a comment. – Jul 23 '12 at 20:08

score -1 · Answer 5 · answered Jul 23 '12 at 20:17

There are several ways to go about solving the issue, but I'm a little uncertain what you mean by "without loops"...

obviously you could use a loop such as:

while (myString.contains("__"))
    myString.replace("__", "_");

I think though that this is what you are saying you're trying to avoid... the catch is though, that I don't believe there is a solution that doesn't involve loops somewhere. The .contains method, as well as the .replace method both use loops in their implementations. To clarify, the following code would also work:

string outputStr = "";
bool underscore = false;
for(int i = 0; i < myString.length; ++i)
{
    if (myString[i] == '_')
    {
        if (underscore == false)
            outputStr += myString[i];
        underscore = true;
    }else outputStr += myString[i];
}

As you can see, this only uses one loop. While this is more efficient, (You would probably want to use a StringBuilder instead of a string for the outputStr variable, if efficiency were an issue) the point is that if you need to look through a string, you're going to have to use a loop, whether it's you who writes the loop or whether you are calling some other method that does it for you.

Multiple replace

5 Answers5