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Problem · Tree

Find the Root of a Directed Tree

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Problem statement

You are given every node identifier in a rooted tree and directed edges [parent, child]. Return the unique root identifier.

The problem statement continues
Pro

Examples

Example 1

nodes = [4,7,9,12]edges = [[7,4],[7,9],[9,12]]return = 7

Every node except 7 appears as a child, so 7 is the root.

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Reported in 1 Amazon interview this week

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FastPrep Pro
Reported in 1 Amazon interview this week

Unlock this recently reported problem

FastPrep Pro gives you full access to interview problems reported within the last week.

  • Full problem statement and constraints
  • 1 more worked example, explained
  • Guided hints and editorial
  • Run your code on real test cases
$9/month

Pro subscription, billed yearly — or $19 month-to-month. Cancel anytime.

Free plan — 2 of 2 free unlocks used this week