Algorithm dossier

  • Category: Tree op
  • Worst-case complexity: O(n)
  • Approach: Iterative
  • Data structure: Tree
  • First formalised: 1960s

Why this snippet is Inorder Traversal

Why inorder traversal. Visit *left subtree, then node, then right subtree*. The iterative form uses an explicit stack (q here): walk down-left pushing every node, then pop and emit, then attempt to descend right. Why this order matters. Inorder on a BST yields values in *sorted* order — that's the property that makes BSTs useful as sorted containers. Preorder and postorder give different (non-sorted) orderings.

How to read a redacted algorithm

Algodle strips identifier names so the snippet has to be read for its shape: the control flow, the data structures it manipulates, the order in which it visits its input. Loops with two pointers crawling toward each other are usually search or partition. A recursion that splits its input in half and recurses on both halves is divide-and-conquer. A priority queue plus graph traversal is almost certainly Dijkstra, Prim, or A*. Six hint columns — category, complexity, approach, data structure, era — let you triangulate even when the snippet itself is opaque.