Tree Traversal (cont)
Consider "visiting" an expression tree like:
![[Diagram:Pic/tree1.png]](Pic/tree1.png)
NLR: + * 1 3 - * 5 7 9 (prefix-order: useful for building tree)
LNR: 1 * 3 + 5 * 7 - 9 (infix-order: "natural" order)
LRN: 1 3 * 5 7 * 9 - + (postfix-order: useful for evaluation)
Level: + * - 1 3 * 9 5 7 (level-order: useful for printing tree)
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