Algorithm 1: SHAP Tree Model Shapley Value Calculation Pseudo-Code $E\left[f\left(x\right)|x_S\right]$.

Inputs: x,S,tree={v,a,b,t,r,d}

Process:

1: if ${\mathit{v}}_{\mathit{j}}$ does not belong to an internal node, then

2:  return w*${\mathit{v}}_{\mathit{j}}$

3: elseif

4:  if $d_j\in S$, then

5:    if$x_{d_j}\le t_j$

6:      return $G\left(a_j,w\right)$

7:    else return $G\left(b_j,w\right)$

9:    endif

8:  else return $\mathrm{G}\left(a_j,w{r}_{a_j}/r_j\right)+\mathrm{G}\left(b_j,w{r}_{b_j}/r_j\right)$

9:   endif 10: endif

Output: $G\left(j,w\right)$