Creating a string from a set of elements from an array in C

Question

Is there a way to create a string of characters from a set of elements taken from a existing array?

Example: say I have an array of four characters

#include <cs50.h>
#include <stdio.h>
#include <string.h>

int main (void)
{
char abcd[] = "abcd";
string sabcd = "0";
}

Is there a way I can create strings with a subset of array elements, such as "ac", "cd" and so on?

Edited: added libraries for clarification.

Technically the array abcd is an array of five characters, since it will include the string terminator. — Some programmer dude
– Some programmer dude, Commented Sep 28, 2017 at 7:14
As for your problem, how about char ac[3] = { abcd[0], abcd[2], '\0' };? You can of course set up the new array ac using a loop and some suitable condition for which characters to include. Perhaps if you try something and have problem with your attempt, then you can come back with a new question including a Minimal, Complete, and Verifiable Example and ask for help with whatever problem you have then. Also take some time to read about how to ask good questions. — Some programmer dude
– Some programmer dude, Commented Sep 28, 2017 at 7:16
Sorry, I thought this short code was enough to make my point. I am working on something bigger but is messy and does not seem right to post it here. I will read your suggestion. Thanks. — Yago Bolívar
– Yago Bolívar, Commented Sep 28, 2017 at 7:29

BLUEPIXY · Accepted Answer · 2017-09-28 07:53:38Z

1

You could always index the characters you wish your substring to have.

For example:

char adb[4] = {abcd[0], abcd[3], abcd[1], '\0'};

Another approach is to use strncpy(), like this:

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

int main (void)
{
    char abcd[] = "abcd";
    char bc[3] = "";
    strncpy(bc, abcd + 1, 2);
    puts(bc);
}

Output:

bc

edited Sep 28, 2017 at 7:53

BLUEPIXY

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answered Sep 28, 2017 at 7:46

gsamaras

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Comments

Jean-François Fabre · Accepted Answer · 2019-05-02 17:35:35Z

1

you can iterate over the array elements like this:

char abcd[] = "abcd";

for(int i=0; i<4; i++){
    for(int j=i; j<4; j++){
        d = abcd[i] + abcd[j];
    }

edited May 2, 2019 at 17:35

Jean-François Fabre♦

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answered Sep 28, 2017 at 7:22

david

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