\documentclass[tikz,border=5pt]{standalone}
\usepackage[utf8]{inputenc}
\usepackage{amssymb}
\usepackage{amsmath}
\usepackage{tikz}
\newcommand{\xx}{1}
\newcommand{\yy}{1}
\newcommand{\stages}[2]{\tikz{\node[shape=circle,draw,inner sep=1pt,fill=#1,minimum size=0.5cm]{\scriptsize{$v_{#2}$}};}}
\newcommand{\leaf}{\tikz{\node[shape=circle,draw,inner sep=1.5pt,fill=white]{};}}
\begin{document}
\begin{tikzpicture}
\renewcommand{\xx}{1.8}
\renewcommand{\yy}{1.2}
\node (v1) at (0*\xx,0*\yy) {\stages{white}{0}};
\node (v2) at (1*\xx,2*\yy) {\stages{pink}{1}};
\node (v3) at (1*\xx,-2*\yy) {\stages{green}{2}};
\node (v4) at (2*\xx,3*\yy) {\stages{red}{3}};
\node (v5) at (2*\xx,1*\yy) {\stages{olive}{4}};
\node (v6) at (2*\xx,-1*\yy) {\stages{yellow}{5}};
\node (v7) at (2*\xx,-3*\yy) {\stages{magenta}{6}};
\node (l1) at (3*\xx,3.5*\yy) {\stages{cyan}{7}};
\node (l2) at (3*\xx,2.5*\yy) {\stages{cyan}{8}};
\node (l3) at (3*\xx,1.5*\yy) {\stages{purple}{9}};
\node (l4) at (3*\xx,0.5*\yy) {\stages{purple}{10}};
\node (l5) at (3*\xx,-0.5*\yy) {\stages{orange}{11}};
\node (l6) at (3*\xx,-1.5*\yy) {\stages{orange}{12}};
\node (l7) at (3*\xx,-2.5*\yy) {\stages{gray}{13}};
\node (l8) at (3*\xx,-3.5*\yy) {\stages{gray}{14}};
\node (l9) at (4*\xx,3.75*\yy){\leaf};
\node (l10) at (4*\xx,3.25*\yy){\leaf};
\node (l11) at (4*\xx,2.75*\yy){\leaf};
\node (l12) at (4*\xx,2.25*\yy){\leaf};
\node (l13) at (4*\xx,1.75*\yy){\leaf};
\node (l14) at (4*\xx,1.25*\yy){\leaf};
\node (l15) at (4*\xx,0.75*\yy){\leaf};
\node (l16) at (4*\xx,0.25*\yy){\leaf};
\node (l17) at (4*\xx,-0.25*\yy){\leaf};
\node (l18) at (4*\xx,-0.75*\yy){\leaf};
\node (l19) at (4*\xx,-1.25*\yy){\leaf};
\node (l20) at (4*\xx,-1.75*\yy){\leaf};
\node (l21) at (4*\xx,-2.25*\yy){\leaf};
\node (l22) at (4*\xx,-2.75*\yy){\leaf};
\node (l23) at (4*\xx,-3.25*\yy){\leaf};
\node (l24) at (4*\xx,-3.75*\yy){\leaf};
\draw[->] (v1) -- node [above, sloped] {\scriptsize{$C=0$}} (v2);
\draw[->] (v1) -- node [below, sloped] {\scriptsize{$C=1$}}(v3);
\draw[->] (v2) -- node [above, sloped] {\scriptsize{$X_1=0$}}(v4);
\draw[->] (v2) -- node [below, sloped] {\scriptsize{$X_1=1$}}(v5);
\draw[->] (v3) -- node [above, sloped] {\scriptsize{$X_1=0$}} (v6);
\draw[->] (v3) -- node [below, sloped] {\scriptsize{$X_1=1$}} (v7);
\draw[->] (v4) -- node [above, sloped] {\scriptsize{$X_2=0$}} (l1);
\draw[->] (v4) -- node [below, sloped] {\scriptsize{$X_2=1$}} (l2);
\draw[->] (v5) -- node [above, sloped] {\scriptsize{$X_2=0$}} (l3);
\draw[->] (v5) -- node [below, sloped] {\scriptsize{$X_2=1$}} (l4);
\draw[->] (v6) -- node [above, sloped] {\scriptsize{$X_2=0$}} (l5);
\draw[->] (v6) -- node [below, sloped] {\scriptsize{$X_2=1$}} (l6);
\draw[->] (v7) -- node [above, sloped] {\scriptsize{$X_2=0$}} (l7);
\draw[->] (v7) -- node [below, sloped] {\scriptsize{$X_2=1$}} (l8);
\draw[->] (l1) -- node [above, sloped] {\scriptsize{$X_3=0$}}(l9);
\draw[->] (l1) -- node [below, sloped] {\scriptsize{$X_3=1$}} (l10);
\draw[->] (l2) -- node [above, sloped] {\scriptsize{$X_3=0$}}(l11);
\draw[->] (l2) -- node [below, sloped] {\scriptsize{$X_3=1$}} (l12);
\draw[->] (l3) -- node [above, sloped] {\scriptsize{$X_3=0$}}(l13);
\draw[->] (l3) -- node [below, sloped] {\scriptsize{$X_3=1$}} (l14);
\draw[->] (l4) -- node [above, sloped] {\scriptsize{$X_3=0$}}(l15);
\draw[->] (l4) -- node [below, sloped] {\scriptsize{$X_3=1$}} (l16);
\draw[->] (l5) -- node [above, sloped] {\scriptsize{$X_3=0$}} (l17);
\draw[->] (l5) -- node [below, sloped] {\scriptsize{$X_3=1$}} (l18);
\draw[->] (l6) -- node [above, sloped] {\scriptsize{$X_3=0$}} (l19);
\draw[->] (l6) -- node [below, sloped] {\scriptsize{$X_3=1$}} (l20);
\draw[->] (l7) -- node [above, sloped] {\scriptsize{$X_3=0$}} (l21);
\draw[->] (l7) -- node [below, sloped] {\scriptsize{$X_3=1$}} (l22);
\draw[->] (l8) -- node [above, sloped] {\scriptsize{$X_3=0$}} (l23);
\draw[->] (l8) -- node [below, sloped] {\scriptsize{$X_3=1$}} (l24);
\end{tikzpicture}
\end{document}