Calculate $$$\textit{dp}(i, j)$$$ the minimum time to reach $$$a_i$$$ such that the bike is at position $$$j$$$ (prepend and append $$$0$$$ to array $$$a$$$ to make the implementation easier). To compute this $$$\textit{dp}$$$ array, consider transitions $$$\textit{dp}(i, j) \Rightarrow \textit{dp}(i + 1, j')$$$, meaning:

1. Walk to $$$j$$$ and take bike
2. Pedal to $$$j'$$$ leave bike there
3. Walk to $$$a_{i + 1}$$$

Code