You can use the `positioning` library to place nodes relative to each other. Like `\node[left=<dimen/factor> of <another node>] {}`. Just give the nodes inside your tree a name and you can get something like this:

 \documentclass{article}
 
 \usepackage{tikz}
 \usetikzlibrary{trees}
 \usetikzlibrary{positioning}
 
 \usepackage{ulem}
 
 \begin{document}
 \begin{tikzpicture}[level distance=1.5cm,
 level 1/.style={sibling distance=4cm},
 level 2/.style={sibling distance=2cm}]
 \node (abc) {$ABC$} child {
 node (AB) {AB} 
 child { node {$A\rightarrow BC$} }
 child { node {$B\rightarrow AC$} }
 } child {
 node (AC) {AC}
 child { node {$A\rightarrow BC$} }
 child { node {$C\rightarrow AB$} }
 } child {
 node (A) {A}
 child { node {$B\rightarrow AC$} }
 child { node {$C\rightarrow AB$} }
 };
 
 \draw node[left=.5 of AB] {\uwave{$A,b$}} edge[<-] (AB);
 \draw node[right=.5 of AB] {$C$} edge[<-] (AB);
 
 \draw node[left=.5 of AC] {\uwave{$A,C$}} edge[<-] (AC);
 \draw node[right=.5 of AC] {$B$} edge[<-] (AC);
 
 \draw node[left=.5 of A] {$BC$} edge[<-] (A);
 \draw node[right=.5 of A] {\uwave{$B,C$}} edge[<-] (A);
 
 \node[left=of abc] {$\uwave{\hspace{3ex}}=(k-1)-\mathrm{Itemsets}$} ;
 \draw node[right=.5 of abc] {\uwave{$AB,AC,BC$}} edge[<-] (abc);
 \end{tikzpicture}
 \end{document}

![result][1]



 [1]: https://i.sstatic.net/0iPrt.png