Do you personally prefer tree problem with $N-1$ pair of integers input where $i^{th}$ input ($u_i$ and $v_i$) denotes the nodes that $i^{th}$ edge connects and all the edges guarantee a tree, or $N-1$ integers input where $i^{th}$ input ($p_i$) indicates that there is an edge that connects node $i+1$ andto node $p_i$, and all the edges also guarantee a tree (usually this comes with the $1 \leq p_i \leq i$ constraint to do that)? I personally prefer the latter.