get all indexes of all occurances of a substring in a string - c

Question

i searched online everywhere but i was unable to find a solution that i could implement in my code, i have some limiting factors to take in accounts, the biggest one is: i cannot use pointers to do this, second one is that i cannot edit before the comment
what i have to do is look for the SEC_B sequence in the adn1 string then save the position of it into a int array to then print it something like this:
Found sequence GTC in: 20 62 69 159 167 196
and yes i did count them manually
i have to do the same with the other sequences, but that doesn't matter as long is i can get it working with one, i can then make it work with all the others
so this is my code:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define SECUENCIA0 "TGGCGTTTGCAGATTACTGCGTCCCTCACAAGGGTGTGAA"
#define SECUENCIA1 "GCTGTGCATTCGCGGCACAAGAGTCCCGGGTCCCTGTAGC"
#define SECUENCIA2 "TTCACCATCCTGTTGTACCTATCAAACCTACCTACAGCTT"
#define SECUENCIA3 "AGTGAAGGATTATGCGATTGGCGAGCATAGTACCGGCCCG"
#define SECUENCIA4 "TCACACCGTCTCATTGGTGGCCGACCTTGGAACTCCGTCA"
#define SEC_B "GTC"
#define SEC_D "GAT"
#define SEC_K "GT"
int main()
{
char adn1[201];
adn1[0]='\0';
strcat(adn1,SECUENCIA0);
strcat(adn1,SECUENCIA1);
strcat(adn1,SECUENCIA2);
strcat(adn1,SECUENCIA3);
strcat(adn1,SECUENCIA4);
//edit from here
return 0;
}

Answer 1

this solution doesn't involve any explicit pointers (no * anywhere) and doesn't edit the line above the comment, i managed to come up with this solution thanks to the answer of zazz (which he deleted for some reson), here's how i've done it
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define SECUENCIA0 "TGGCGTTTGCAGATTACTGCGTCCCTCACAAGGGTGTGAA"
#define SECUENCIA1 "GCTGTGCATTCGCGGCACAAGAGTCCCGGGTCCCTGTAGC"
#define SECUENCIA2 "TTCACCATCCTGTTGTACCTATCAAACCTACCTACAGCTT"
#define SECUENCIA3 "AGTGAAGGATTATGCGATTGGCGAGCATAGTACCGGCCCG"
#define SECUENCIA4 "TCACACCGTCTCATTGGTGGCCGACCTTGGAACTCCGTCA"
#define SEC_B "GTC"
#define SEC_D "GAT"
#define SEC_K "GT"
int main()
{
char adn1[201];
adn1[0]='\0';
strcat(adn1,SECUENCIA0);
strcat(adn1,SECUENCIA1);
strcat(adn1,SECUENCIA2);
strcat(adn1,SECUENCIA3);
strcat(adn1,SECUENCIA4);
//edit below here
printf("---- Búsqueda de secuencias B, D y K dentro del adn1 ------\n");
int PosicionesB[20];
int bs = 0;
int i, l1, l2;
l1 = strlen(adn1);
l2 = strlen(SEC_B);
for(i = 0; i < l1 - l2 + 1; i++) {
if(strstr(adn1 + i, SEC_B) == adn1 + i) {
PosicionesB[bs] = i;
bs++;
i = i + l2 -1;
}
}
printf("Found sequence GTC in:");
for(int i = 0; i < bs;i++){
printf(" %d",PosicionesB[i]);
}
return 0;
}

Answer 2

It's as simple as this:
#include <stdio.h>
#include <stdint.h>
#include <string.h>
void print_indices_substr(const char *str, const char *substr)
{
char *pstr;
printf("Indices: { ");
for (pstr = (char *)str; (pstr = strstr(pstr, substr)) != NULL; pstr = &pstr[1])
printf("%lu, ", (uintptr_t)pstr - (uintptr_t)str);
printf("}\n");
}
Basically, the function strstr returns a pointer to the first occurrence of 'substr' in 'str' or NULL if no occurrence was found. We can use this pointer in a for loop, and the index will be pstr - str, as you can see in the function above. Example:
int main()
{
const char my_string[] = "ABCDABCD";
print_indices_substr(my_string, "ABCD");
return 0;
}
Output:
Indices: { 0, 4, }