CSES 1131 Tree Diameter - Two Approaches Compared

You now know $2$ ways to find tree diameter:

$1.$ DP approach (LC $543$): Recurse on the tree, compute heights, track the maximum left + right sum. Works naturally on binary trees with pointer-based nodes.

$2.$ Double BFS (CSES $1131$): Run BFS twice from endpoints. Works on any tree given as an adjacency list. Simpler when you do not need subtree information.

Both run in $O(n)$ time. The Tree Diameter & Center section covers both in full detail with implementations and walkthroughs.