C program to remove consecutive repeated characters from string-CodePudding

The code: https://pastebin.com/nW6A49ck

The problem: Lets say I have the string 'Hello' as an input..I want the two l's to be both removed (not only 1)..Same for 'Helllo' (I want the 3 l's to be removed and not just the 2 l's)..How can I do that?

if(str[i]==str[i 1])
    {
        /*shift all characters*/
        for(j=i;j<(len-len1);j  )
            str[j]=str[j 1];
        len1  ;
    }

Maybe I can count the times every character is repeated and then in line 28 replace 1 with the the times a character is repeated? But how can I implement this to the code?

CodePudding user response：

This code snippet should remove all consecutive characters out of your string (note that some C compilers won't let you declare variables within the internal blocks):

for (int i=0; i<len; i  ) {
    int j = i, repeats = 1;
    while (j < len-1 && str[j] == str[  j])
    {
        repeats  ;
    }
    if (repeats > 1) {
        for (j = i; j < len - repeats; j  )
        {
            str[j] = str[j   repeats];
        }
        len -= repeats;
        i--;
        str[len] = '\0';
    }
}

CodePudding user response：

Links are discouraged, instead, you should post the contents of link. Also, for such kind of problem, I will suggest first come up with an appropriate algorithm and then implement it. At time, you will find it much more easier than taking someone else's code and making changes to it make it work as per your need.

Algorithm:

Step I: Record the position where the letter to be written in the string (calling this position - P). Initially, it will be start of string.

Step II: If current processing character is same as it's next character, then

Dont make any change in P.
Set a flag to skip next character (calling this flag - F).

Step III: If current processing character and next character are different, then

If flag F is set, skip this character, reset flag F and don't change P.
If flag F is not set then write this character at position P in the string and set P to next position.

Step IV: Move to next character in the string and go to Step II.

Implementation:

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

void remove_all_consecutive_dup_chars (char * pstr) {
    if (pstr == NULL) {
        printf ("Invalid input..\n");
        return;
    }

    /* Pointer to keep track of position where next 
     * character to be write.
     */
    char * p = pstr;
    int skip_letter = 0;

    for (unsigned int i = 0; pstr[i] ;   i) {
        /* Using tolower() to identify the consecutive characters 
         * which are same and only differ in case (upper/lower).
         */
        if ((tolower (pstr[i]) == tolower (pstr[i   1]))) {
            skip_letter = 1;
            continue;
        }

        if (skip_letter) {
            skip_letter = 0;
        } else {
            *p   = pstr[i];
        }
    }

    /* Add the null terminating character. 
     */
    *p = '\0';
}

int main (void) {
    char buf[256] = {'\0'};

    strcpy (buf, "WELL, well, welLlLl....");
    printf ("%s ----> ", buf);
    remove_all_consecutive_dup_chars (buf);
    printf ("%s\n", buf);

    strcpy (buf, "Hello");
    printf ("%s ----> ", buf);
    remove_all_consecutive_dup_chars (buf);
    printf ("%s\n", buf);

    strcpy (buf, "Helllo");
    printf ("%s ----> ", buf);
    remove_all_consecutive_dup_chars (buf);
    printf ("%s\n", buf);

    strcpy (buf, "aAaaaA    ZZz");
    printf ("%s ----> ", buf);
    remove_all_consecutive_dup_chars (buf);
    printf ("%s\n", buf);
    
    return 0;
}

Output:

# ./a.out
WELL, well, welLlLl.... ----> WE, we, we
Hello ----> Heo
Helllo ----> Heo
aAaaaA    ZZz ---->

CodePudding user response：

You could make a function to remove the ranges with equal characters by copiing character by character to a separate pointer in the string that you do not step forward if repeating characters are found:

void foo(char *str) {
    for(char *wr = str; (*wr = *str) != '\0';) {
          str;
        if(*wr != *str)   wr; // next not equal, step wr
        else do   str; while(*wr == *str); // skip all equal characters
    }
}