\begin{tikzpicture}[x=1cm,y=.90cm,font=\small,>=Latex,
 profile/.style={circle,draw,fill=white,minimum size=15pt,inner sep=0pt},
 used/.style={fill=blue!12,draw=blue!65!black},
 last/.style={fill=orange!15,draw=orange!80!black}]
\node[anchor=west] at (-.35,4.55) {(a) Integer vectors};
\draw[->] (-.35,0)--(3.75,0) node[right] {$x_1$};
\draw[->] (0,0)--(0,3.6) node[above] {$x_2$};
\foreach \r in {1,2,3}{\draw[dashed,black!30] (0,\r)--(\r,0);}
\foreach \x/\y in {0/0,1/0,0/1,2/0,1/1,0/2}{\node[profile,used] at (\x,\y) {2};}
\node[profile,last] at (3,0) {2};
\node[profile,last] at (2,1) {1};
\node[profile] at (1,2) {0};
\node[profile] at (0,3) {0};
\foreach \t in {0,1,2,3}{\node[below,inner sep=1pt] at (\t,-.32) {$\t$};}
\foreach \t in {1,2,3}{\node[left,inner sep=1pt] at (-.32,\t) {$\t$};}
\node[anchor=west] at (5.25,4.55) {(b) Count and cost by layer};
\node at (5.65,3.4) {$r$};
\node at (8.2,3.4) {occurrences};
\node at (11.85,3.4) {cost};
\foreach \r/\y/\cap/\occ/\val in {0/2.8/2/2/0,1/2.05/4/4/4,2/1.3/6/6/12,3/.55/8/3/9}{
 \node at (5.65,\y) {$\r$};
 \foreach \j in {1,...,\cap}{
  \draw[black!45] ({6.25+.5*(\j-1)},\y-.18) rectangle ++(.38,.36);
 }
 \foreach \j in {1,...,\occ}{
  \ifnum\r<3 \def\col{blue!65!black}\else\def\col{orange!80!black}\fi
  \fill[\col] ({6.25+.5*(\j-1)},\y-.18) rectangle ++(.38,.36);
 }
 \node at (11.85,\y) {$\r\cdot\occ=\val$};
}
\draw[black!50] (5.25,-.02)--(12.6,-.02);
\node at (8.05,-.47) {$2+4+6+3=15$};
\node at (11.85,-.47) {$25$};
\end{tikzpicture}