Algorithm dossier

  • Category: Sort
  • Worst-case complexity: O(n²)
  • Approach: Iterative
  • Data structure: Array
  • First formalised: 1950s

Why this snippet is Selection Sort

Why selection sort. Outer loop fixes a position i. Inner loop scans the rest of the array tracking the index of the running minimum k. After the scan, a single swap drops the minimum into position. Distinguishing feature. One swap per outer iteration — n swaps total. Bubble sort would do up to n swaps *per* outer iteration. Insertion sort doesn't swap, it slides.

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.