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Each node in a tree is the root of a subtree beginning at that node. This subtree property is conducive to recursion because recursion generally involves solving a problem in terms of similar subproblems and a base case.

From

Cover of Programming Interviews Exposed: Secrets to Landing Your Next Job, 3rd Edition

Note

Important. Thinking of child nodes as the root of a subtree. Recursion general cases and base cases.