Remove consecutive duplicate characters from a string in python

Question

Hey I was trying to write a program which will remove the consecutive duplicate characters from a string.

for example:
string->aabbccde
first iteration: bbccde
second iteration: ccde
third Iteration: de

and de is the answer.

following is the program I wrote.

a = "aabbcs"
def remove_dups(st,ind):
    print st, ind
    st = st.replace(st[ind], "")
    print st, "in dups"
    find_dups(st)

def find_dups(text):
    s=text
    print s, "in find"
    ln = len(s)
    print ln
    fg = 0
    ind = 0
    if ln==1:
        print s, 'len'
        return s
    for i in range(0,ln-1):
        if(s[i]==s[i+1]):
            ind = i
            remove_dups(s,ind)
    print s, 'check'        
    return s

ans = find_dups(a)
print 'answer', ans

and following is the output I am getting

aabbcs in find
6
aabbcs 0
bbcs in dups
bbcs in find
4
bbcs 0
cs in dups
cs in find
2
cs check
bbcs check
aabbcs 2
aacs in dups
aacs in find
4
aacs 0
cs in dups
cs in find
2
cs check
aacs check
aabbcs check
answer aabbcs

here above we have got cs but still answer is coming original string, I can understand it is because of recursion, but unable to understand how to resolve the issue. A little help would be appreciated. Thanks!

Fujiao Liu · Accepted Answer · 2016-11-20 14:26:42Z

3

python have some easier way to do this, one of them:

>>> dup_string = 'aabcbccde'
>>> from itertools import groupby
>>> ''.join([x for x,y in groupby(dup_string) if sum(1 for i in y)<2])
'bcbde'
>>> dup_string = 'aabbccde'
>>> ''.join([x for x,y in groupby(dup_string) if sum(1 for i in y)<2])
'de'
>>>

edited Nov 20, 2016 at 14:26

answered Nov 20, 2016 at 14:10

Fujiao Liu

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2 Comments

Jon Clements Over a year ago

I suspect that a string ending in ded will require an output of ded since there're not immediately consecutive letters. This will output de still... and abcbca will return an empty string and there's nothing consecutive at all...

Fujiao Liu Over a year ago

this time should be ok.

yeedle · Accepted Answer · 2016-11-28 15:56:49Z

2

If you're going to call the find_dups method recursively, you might as well get rid of the for loop. Just remove the consecutive duplicates as soon as you find them, and then recursively call find_dups again on the newly returned string.

a = "aabbcs"
def remove_dups(st,ind):
     return st.replace(st[ind:ind+1], "")


def find_dups(text, i):
    if len(text)-1 == i:
        return text
    if(text[i]==text[i+1]):
        text = remove_dups(text,i)
        text = find_dups(text, i)
    else:
        text = find_dups(text, i+1)
    return text

ans = find_dups(a, 0)
print "answer", ans

edited Nov 28, 2016 at 15:56

answered Nov 20, 2016 at 14:20

yeedle

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Comments

Batman · Accepted Answer · 2016-11-20 14:03:15Z

1

Your line remove_dups(s,ind) is the problem. It's not doing anything with the returned value. If you read through your code, in the top level function call you're assigning s=text at the top, then returning s at the bottom, without ever modifying the value of s. The clue is that you're printing the original text last, after you've printed the correct answer.
Try s = remove_dups(s, ind)

answered Nov 20, 2016 at 14:03

Batman

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1 Comment

Umesh Kaushik Over a year ago

thanks I added s = remove_dups(s,ind) and this s = find_dups(s) rest it worked

saurabh baid · Accepted Answer · 2016-11-20 14:09:55Z

1

You could easily do it using re.sub

import re
str = "aaaabbcccdddx"
print(re.sub(r"(.)\1+", '', str))

OP

edited Nov 20, 2016 at 14:09

answered Nov 20, 2016 at 14:06

saurabh baid

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1 Comment

Jon Clements Over a year ago

Almost - you want '' though as the replacement string so the output matches the de the OP is expecting...

hyades · Accepted Answer · 2016-11-20 15:01:57Z

1

You should be returning the values of the string, since these are passed by copies. Also once you are done with remove_dups you should break out since you are no longer interested in the same you just modified.

a = "aabbcs"
def remove_dups(st,ind):
    print st, ind
    st = st.replace(st[ind], "")
    print st, "in dups"
    return find_dups(st)

def find_dups(text):
    s=text
    print s, "in find"
    ln = len(s)
    print ln
    fg = 0
    ind = 0
    if ln==1:
        print s, 'len'
        return s
    for i in range(0,ln-1):
        if(s[i]==s[i+1]):
            ind = i
            s = remove_dups(s,ind)
            break
    print s, 'check'        
    return s
ans = find_dups(a)
print 'answer', ans

edited Nov 20, 2016 at 15:01

answered Nov 20, 2016 at 14:16

hyades

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Comments

Ali tariq · Accepted Answer · 2016-11-20 14:50:16Z

0

bellow is your function to do the job

def remove_duplicates(str):
  integer=0
  while integer<len(str)-1:
      if str[integer]==str[integer+1]:
          str=str.replace(str[integer]," ",2)
      integer=integer+1    
  str=str.replace(" ","")
  print(str)

you can include the print statements that i left out!

answered Nov 20, 2016 at 14:50

Ali tariq

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Comments

Maulik Madhavi · Accepted Answer · 2020-10-04 08:00:00Z

0

For general list:

mylist = [['a'], ['a'], ['a'], ['b'], ['b'], ['c'], ['d'], ['e'], ['f'], ['a'], ['a']]
idx = 0
while True:
    if idx == len(mylist) - 1:
         break
    if mylist[idx] == mylist[idx + 1]:
         del mylist[idx + 1]
         idx = idx
    else:
         idx = idx + 1

answered Oct 4, 2020 at 8:00

Maulik Madhavi

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