Remove the duplicate from a String Using Pointers

Question

#include<stdio.h>
char *removedps(char *x)
{
    int Ar[256] = {0};
    int ip=0;
    int op=0;
    char temp;
    while(*(x+ip))
    {
       temp  = (*(x+ip));
       if (!Ar[temp])  {
         Ar[temp] = 1;
         *(x+ip) = *(x+op);
         op++;
       }
       ip++;
       *(x+op) = '\0';
    }
  return x;
}

int main()
{
  char lo[] = "0001";
  printf("%s",removedps(lo));    
}

My code is not working I have tried hard to see the error All I GET IS the first character . My idea is simple make an array of 256 places insert Zero into them Then insert 1 for each character inside the string (on that position of the array)

Do they have to be consecutive ?

cnicutar
– cnicutar

2012-01-15 19:53:19 +00:00
Commented Jan 15, 2012 at 19:53 — cnicutar
– cnicutar, Commented Jan 15, 2012 at 19:53
not necessary :they can be anywhere :the re can be anywhere

user1149549
– user1149549

2012-01-15 19:55:55 +00:00
Commented Jan 15, 2012 at 19:55 — user1149549
– user1149549, Commented Jan 15, 2012 at 19:55

CashCow · Accepted Answer · 2012-01-15 20:00:05Z

1

your assignment looks to be the error here.

op is "out postiion", ip is "in position"

so it should be

*(x+op) = *(x+ip);

not the other way.

answered Jan 15, 2012 at 20:00

CashCow

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Comments

Keith Nicholas · Accepted Answer · 2012-01-15 20:37:23Z

1

because *(x+op) = '\0';

is always run every iteration of the loop.

I'd probablly do it more like this ( using your method, which I probablly wouldn't use personally)

char *removedps(char *x)
{
    int Ar[256] = {0};
    char* start = x;
    while(*x)
    {       
        if (Ar[*x])   
        {  // remove the repeated character 
           memmove(x, x+1, strlen(x));
        }   
        else
        {
            Ar[*x] = 1;
            x++;
        }       
    }
    return start;
}

also, I'd name it remove_duplicate_chars or something, not a fan of cryptic abbreviations.

edited Jan 15, 2012 at 20:37

answered Jan 15, 2012 at 19:55

Keith Nicholas

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2 Comments

user1149549 Over a year ago

I have removed and replaced the statement :Still facing problems

dreamlax Over a year ago

int Ar[256] = {0}; is neater and more concise than using memset I think, chances are the = {0} may end up being a call to memset anyway, but I think it looks nicer.

asaelr · Accepted Answer · 2012-01-15 19:55:07Z

0

At the end of the loop, you do *(x+op)='\0';, and then, in the next iteration, you do *(x+ip)=*(x+op);, so from the 2sd iteration, you put there 0.

try do something like:

for (op=ip=0;x[ip];ip++) {
 if (!Ar[x[ip]]++) x[op++]=x[ip];
}
x[op]=0;

answered Jan 15, 2012 at 19:55

asaelr

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