How to remove a certain digit from a number multiple times.Algorithm

Razvanq · 08-28-2012, 01:35 PM

Hi. I would like some help with this algorithm. So i have been trying for about one hour now to solve this simple algorithm (or at least that is what i thought when i first looked into it).

I need to remove a certain digit from a number which repeats itself multiple times.
As an example if our number is 52753 and we need to remove the digit 5 (what number needs to be deleted is typed from the keyboard). It should pop on the screen this number 273.

I have been trying to get the number in a vector and try to work it out from there but i didn't get anywhere this way. Also been trying to play around with / and % but i still didn't solve it.
I am pretty sure the algorithm isn't as complicated as i have thought but i just don't seem to be able to get on the good path to solve it.

Help would be greatly appreciated. Thank you in advance

danielbmartin · 08-28-2012, 01:51 PM

Quote:

Originally Posted by Razvanq

As an example if our number is 52753 and we need to remove the digit 5 (what number needs to be deleted is typed from the keyboard). It should pop on the screen this number 273.

sed could be the "heart" of your solution.

Code:

echo "52753" | sed 's/5//g'

This takes the input (which could be a whole file of data) and replaces every 5 with the null string.

Code:

sed 's/5//g' < $InFile > $OutFile

Daniel B. Martin

Razvanq · 08-28-2012, 03:48 PM

Thanks for the replay !
Well the commands that you posted aren't something that i have learned so i was wondering if there is a way to do this using commands like / or % in a while(). Or something similar.

suicidaleggroll · 08-28-2012, 04:32 PM

What language are you trying to do this in?

In bash:

Code:

$ var=52753
$ echo ${var//5/}
273

PTrenholme · 08-28-2012, 06:06 PM

Assuming you're using bash, and the string is in a variable called string, then short=${string//5} should create a short variable without any fives in it.

That doesn't address the question "How to identify the repeated digits?," but your "vector" method seem a reasonable approach.

If you don't need to use bash, here's a gawk program you could use

Code:

#!/bin/gawk -f
{
  delete count
  n=split($0,digit,"")
  for (i=1;i<=n;++i) {
    count[digit[i]]++
  }
  j=0
  for (i=1;i<=n;++i) {
    if (count[digit[i]]==1) {
      ++j
      printf("%d", digit[i])
    }
  }
  if (j) print " <- " $0
}

(If you don't want the source number, replace the if (j) print " <- " $0 with a if (j) print ""; else print)

With that change, I get the following with ten random five-digit numbers:

Code:

$ cat r10
23722
69450
92719
67290
42707
88180
13841
44521
06246
04079
$ gawk -f remove_dups.gawk r10
37
69450
271
67290
420
10
384
521
024
479

(You can make the gawk program executable by a chmod +x remove_dups.gawk where, of course, the remove_dups.gawk is whatever you named your copy of the program.)

Note: That program will remove any duplicated character(s) in the input file, not just digits.

<edit>
By the way, the probability that a random five digit number will have a all digits different is about 1/3 (It's exactly 0.9*0.8*0.7*0.6.), so the two I got out of ten is about right.)
</edit>

Razvanq · 08-29-2012, 03:34 PM

I am writing in c++. Using Mingw developer studio to write in.
I think i understand. Thanks for help