Euler Traversal & LCA in a Tree

Euler Traversal

  • Start as ROOT --> Subtree-1 --> ROOT --> Subtree-2 --> ROOT --> Subtree-3 --> ROOT
  • Recurse at each subtree as above
  • All nodes of a subtree appear together, contiguously in the traversal.

Why Euler Traversal Gets LCA?

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Assume we want LCA of a node u in subtree a and node v in subtree c. A Euler walk of the tree will have all nodes of the subtree a followed by the LCA node ROOT and all the nodes of subtree c.

Thus Euler walk/ traversal of a tree will always have the LCA for any two nodes.


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