$$\begin{aligned}
\mathscr{L}\{f(t)\} &=\int_{0}^{1}-e^{-s t} d t+\int_{1}^{\infty} e^{-s t} d t=\left.\frac{1}{s} e^{-s t}\right|_{0} ^{1}-\left.\frac{1}{s} e^{-s t}\right|_{1} ^{\infty} \\
&=\frac{1}{s} e^{-s}-\frac{1}{s}-\left(0-\frac{1}{s} e^{-s}\right)=\frac{2}{s} e^{-s}-\frac{1}{s}, \quad s>0
\end{aligned}$$