DFS for Ternary Tree

public static String[] ternaryTreePaths(Node root) {
    if(root== null ) return null;
    ArrayList<String> al = new ArrayList<String>();
    ArrayList<String> res = new ArrayList<String>();
    dfs(root, al, res);
    return res.toArray(new String[res.size()]);
}

public static void dfs(Node root, ArrayList<String> list, ArrayList<String> res){
    boolean isNoChild = true;
    for(Node child : root.children){
        if(child!=null){
            isNoChild= false;
        }
    }
    if(isNoChild){
        StringBuilder sb = new StringBuilder();
        for(String val : list)
            sb.append(val + "->");
        sb.append(root.val);
        if(sb.length()>1){
            res.add(sb.toString());
        }
        return;
    }
    list.add(Integer.toString(root.val));

    for(Node child: root.children){
        if(child!=null)
            dfs(child, list,res);
    }
    if(list.size()>0){
        list.remove(list.size()-1);
    }

}

The above algorithm tells how we can traverse through ternary tree or any tree using dfs technique. We simply need to put for loop for all children of a node where we generally use node.left and node.right for binary tree.

Whenever we want to terminate condition for which there is no children of a node then also use for loop to check whether children list is null or list is empty.