Moderate Trees Question 108 of 224

How do you check whether a root-to-leaf path sums to a target?

DSA interview set · Speak this in 60–90 seconds · Faridabad & Delhi NCR

StackLIFOlast in, first out

QueueFIFOfirst in, first out

DFS subtracting the node value, succeeding when you hit a leaf and remaining target is zero.

Why interviewers care about Trees:

This is a process

question about Trees.

Panels listen for order,

trade-offs, and what you would actually do on a DSA project - not buzzwords.

Stay structured

Name the idea, why it exists, then one short example.

Close cleanly

End with when you use it and one common pitfall.

Before you speak the answer, walk the interviewer through these steps:

1
DFS subtracting the node
value, succeeding when you hit a leaf and remaining target is zero.
2
Time is O(n) and
space is O(h).
3
BFS with remaining sums
on a queue is equivalent and avoids recursion depth issues on skewed trees.
4
Give an example
One tiny concrete case you can say aloud.
5
Common mistake
What juniors usually get wrong.
6
Close
When you pick this over the alternative.

Here's a short line you can speak, broken into clear beats:

Say this line

“Time is O(n) and space is O(h).”

Break into beats

TimeisOnandspace

Speaking order

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Note: Adapt this scaffold to your own project — keep it under 60–90 seconds.

DFS subtracting the node value, succeeding when you hit a leaf and remaining target is zero. Time is O(n) and space is O(h).