swap_strings_v2.c

/*

    swap_strings_v2.c

    https://web.facebook.com/groups/c.programing/permalink/1558823557609822/

    A string consists of two strings separated by ';' .
    The task is to change the order of the two stings.

    Version without string.h .


    You can find all my C programs at Dragan Milicev's pastebin:

    https://pastebin.com/u/dmilicev

*/

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

char *swap(char s[] )
{
    int i, j, length;
    char delimiter = ';';

    i=0;                                        // calculate length of s, implementation of strlen()
    length=0;
    while( s[i] != '\0' )
    {
        length++;
        i++;
    }

    char tmp[length+1], first[length+1], second[length+1];  // declare 3 strings

    i=0;                                        // get first string from string s
    j=0;
    while( s[i] != delimiter )
    {
        first[j] = s[i];
        i++;
        j++;
    }
    first[j] = '\0';                            // finish string first

    i++;                                        // get second string from string s
    j=0;
    while( s[i] != '\0')
    {
        second[j] = s[i];
        i++;
        j++;
    }
    second[j] = '\0';                           // finish string second

    i=0;                                        // put second string in string s
    j=0;
    while( second[i] != '\0')
    {
        s[j] = second[i];
        i++;
        j++;
    }

    s[j] = delimiter;                           // put delimiter in string s

    i=0;                                        // put first string in string s
    j++;
    while( first[i] != '\0')
    {
        s[j] = first[i];
        i++;
        j++;
    }
    s[j] = '\0';                                // finish string s

    return s;
}


int main(void)
{
    char str[] = "first;second";

    printf("\n before: |%s| \n", str );

    swap(str);

    printf("\n after:  |%s| \n", str );

    printf("\n again:  |%s| \n", swap(str) );


    return 0;
}