list_sub_string_of_3_strings.c

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

char x[3][100] = {"abc", "de", "mnt"};
FILE *fi, *fo;

void recurse(int i, char res[100])
{
    if (i == 3){
        fprintf(fo, "%s \n", res);
        return;
    }
    for (int j = 0; j < strlen(x[i]); ++j){
        strncat(res, &x[i][j], 1);
        recurse(i+1, res);
        res[strlen(res)-1] = '\0';
    }
}

int main()
{
    fi = fopen("in", "r");
    fclose(fi);

    fo = fopen("out", "w");
    char res[100] = "";
    recurse(0, res);
    fclose(fo);
    return 0;
}
// NOLINTEND