maxLength
to 0.dfs
that takes a node p
, its parent node parent
, and the current length
of the consecutive sequence.p
is null, return immediately.p
is consecutive with its parent (i.e., p.val == parent.val + 1
), increment length
; otherwise, reset length
to 1.maxLength
with the maximum of its current value and length
.dfs
for the left and right children of p
, passing the current node as the parent and the updated length
.maxLength
as the result.