for(int i = 0;i<n;i++){
    //insert codek mtaa el région

    int found = 0;
    do{
        found = 0;
        printf("Saisir un code unique (centre %d) :\n",i);
        scanf("%d",&_code);
        for(int j=0;j<i;j++){
            if(centre[j].codeunq == _code){
                found = 1;
            }
        }
    }
    while(found == 1);
    centre[i].codeunq = _code;
}