How to concat integer and string inside recursive function in C

Question

guys, I want to make a program to generate all combination elements. for example if user input (n) = 3, so the output must be like this :

I have a problem to concat integer and string inside recursive function..

Code :

#include <stdio.h>

void rekursif(int m, int n, char angka[100]){
    int i;
    for(i=m; i<=n; i++){
        sprintf(angka, "%s %d", angka, i);
        printf("%s \n", angka);
        rekursif(i+1,n,angka);
    }
}

int main(){
    rekursif(1,5,"");
    return 0;
}

when I run the program, command prompt is not responding. I guess, the problem is in concation ( sprintf(angka, "%s %d", angka, i); ) please help me to solve this problem. thank you :)

Yu Hao · Accepted Answer · 2014-05-18 12:32:13Z

1

By passing "" as the function argument, you are trying to modify a string literal, which is undefined behavior. Instead, do:

int main(){
    char str[100];
    rekursif(1, 5, str);
    return 0;
}

Be careful with buffer overflow in practice.

answered May 18, 2014 at 12:32

Yu Hao

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3 Comments

stranger Over a year ago

Thanks for your response. Command prompt is running well. But if I input n = 3 the result is like this 1 12 123 1233 12332 123323 1233233 I realize that I was wrong, the variable angka must be reset in specific condition. is there another way to solve this problem beside sprintf function? thanks

Yu Hao Over a year ago

@stranger Since you can debug the program now, it's best that you try it first before asking for help.

stranger Over a year ago

Sorry, I just try debug the program right now, and it solved. Thanks. I just need to back up the variable angka into another variable before concation.

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