Trier une chaine de caractere des codons selon leurs occurrences

#include <stdio.h>
#include <string.h>
int Extract_Codon(char chaine[], char codon[][4])
{
    int nb_codon = strlen(chaine)-2;
    for (int i = 0; i<nb_codon; i++)
    
    {
        strncpy(codon[i], chaine, 3);
        codon[i][3] = '\0';
        chaine++;
    }
    return nb_codon;
}

int main(void)
{
    char chaine [100] = "ACGACG";
    char listCodon[100][4];
    int nb_codon = Extract_Codon(chaine, listCodon);
    char tableau[nb_codon][2];
    int occ=0;
    for(int i=0; i<nb_codon; i++){
        int occ=0;
        for (int j=0; j<nb_codon; j++){
            if (strcmp(listCodon[i],listCodon[j])==0){
                occ++;
                
            }
        }
        printf("%s\n %d\n",listCodon[i], occ);
      
    }
}

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
 
typedef struct
{
    char nom[4];
    int nombre;
} Codon;
 
void ExtractFirstCodon(char codon[], char chaine[])
{
    strncpy(codon, chaine, 3);
    codon[3] = '\0';
}
 
void InsertCodon(Codon listCodon[], char codon[], int position)
{
    listCodon[position].nombre=1;
    strcpy(listCodon[position].nom, codon);
}
 
int CompteCodons(char chaine[], Codon listCodon[])
{
    int nb_codon = strlen(chaine)-2;
    char codon[4];
    int indiceCodon = 1;
 
    for(int i=0; i<nb_codon; i++)
    {
        ExtractFirstCodon(codon, chaine);
        if(i==0)
        {
            InsertCodon(listCodon, codon, 0);
            chaine++;
            continue;
        }
 
        int codonAbsent = 1;
 
        for(int j=0; j<i; j++)
        {
            if(strcmp(listCodon[j].nom, codon)==0)
            {
                listCodon[j].nombre++;
                codonAbsent=0;
            }
        }
 
        if(codonAbsent)
        {
            InsertCodon(listCodon, codon, indiceCodon);
            indiceCodon++;
        }
 
        chaine++;
    }
    return indiceCodon;
}
int Tri_occ(const void *cd1, const void *cd2)
{
   int compar= ((Codon*)cd1)->nombre - ((Codon*)cd2)->nombre;
   if (compar==0)
    {
       return strcmp(((Codon*)cd1)->nom , ((Codon*)cd2)->nom)   ;  
        }
    else
        return -compar;
}



int main(void)
{
    char chaine [100] = "TACGACGCGACTACGTCGTACG";
    Codon listCodon[64];
 
    int nbCodon = CompteCodons(chaine, listCodon);
    qsort(listCodon, nbCodon, sizeof(Codon), Tri_occ);
    for(int i=0; i<nbCodon; i++)
        printf("%s --> %d\n", listCodon[i].nom, listCodon[i].nombre);
 
    return 0;
}