This is the working code.
You can try with yours
$id = get_the_ID(false);
$categories = get_the_category();
$parents = array();
$childs = array();
foreach($categories as $cat){
if($cat->parent == 0){
$parents[] = $cat;
} else {
$childs[] = $cat;
}
}
$i = 1;
echo "<div class="sub-container">";
foreach($parents as $parent){
if($i>3){
$i=1;
echo "<div class="clr"></div>";
echo "<hr class="mt25">";
echo "<div class="one3 gray-text mar-none">";
} else {
echo "<div class="one3 gray-text">";
}
echo "<h3 class="title fs14">".$parent->name."</h3>";
echo "<div class="fs10">";
foreach($childs as $child){
if($child->parent == $parent->cat_ID){
echo "<div class="fs14 child-cat"><a href="https://wordpress.stackexchange.com/questions/192357/.get_category_link( $child->cat_ID).">" . $child->name . "</a></div>";
}
}
echo "</div></div>";
$i++;
}
echo '</div>';