C remove duplicates character in char array

Question

In a text file I have "abbcccdddd". I want to store "abcd" in an array.

Before: tx[0] = a, tx[1] = b, tx[3] = c, tx[6] = d

After: tx[0] = a, tx[1] = b, tx[2] = c, tx[3] = d

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

void main() 
{
    FILE *fp = fopen("D:\\C#\\Zip\\Text001.txt", "r");
    char x;
    int size;
    int j, k;
    int i = 0;

    fseek(fp, 0, SEEK_END);
    size = ftell(fp);
    fseek(fp, 0, SEEK_SET);
    char tx[size];
    x = fgetc(fp);

    while (x != EOF)
    {
        tx[i] = x;
        printf("%c", tx[i]);
        x = fgetc(fp);
        i++;
    }
}

Your attempt appears to be no attempt at all. It simply reads in the data from a file. That gets you to the starting point you describe. — John Bollinger
– John Bollinger, Commented Nov 30, 2016 at 18:38
It would be easier to de-duplicate as you read the characters from the file, so that the array never has runs of duplicate characters in the first place. You could do that with a small modification to what you already have. — John Bollinger
– John Bollinger, Commented Nov 30, 2016 at 18:41
If the input is aabbccaabbcc, do you want the output to be abcabc or abc? The first is a lot easier than the second. — Jonathan Leffler
– Jonathan Leffler, Commented Nov 30, 2016 at 21:43

MayurK · Accepted Answer · 2016-11-30 18:54:43Z

1

remove_repeatation() will do this.

void remove_repeatation(char *str)
{
    char flag[256] = {0}; //Assuming sizeof char is 8. So max 256 different characters.
    int  i            = 0;
    int  j            = 0;

    for(i=0; str[i] != '\0';)
    {
        if(0 == flag[str[i]]) //Check if character is already found.
        {
            flag[str[i]] = 1; //If a character is found for the first time, enable corresponding flag.
            i++; //Go to next byte in the array.
        }
        else
        {
            for(j=i; str[j] != '\0'; j++)
                str[j] = str[j+1]; //If repeated character, shift the array entries to 1 byte left.
        }
    }
}

answered Nov 30, 2016 at 18:54

MayurK

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3 Comments

Nisse Engström Over a year ago

FYI: Someone made a suggestion to simplify your code. See here.

MayurK Over a year ago

@Aniket Khaire: I don't know why I am not able to approve your edits. Please post it as a separate answer. It is better than my solution.

Nisse Engström Over a year ago

The review was completed when three reviewers rejected it due to the substantial changes to the code.

daBigBug · Accepted Answer · 2016-12-05 03:10:23Z

0

Edit to above code by MayurK:

char* remove_repeatation(char *str)
{
    char flag[256] = {0}; //Assuming sizeof char is 8. So max 256 different characters.
    int  i            = 0;
    int  j            = 0;

    for(i=0; str[i] != '\0'; i++)
    {
        if(0 == flag[str[i]]) //Check if character is already found.
        {
            flag[str[i]] = 1; //If a character is found for the first time, enable corresponding flag.
            str[j] = str[i];
            j++;
        }
    }
    str[j] = '\0';
    return *str;
}

edited Dec 5, 2016 at 3:10

answered Dec 5, 2016 at 2:15

daBigBug

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