See how your code actually runs.
Step through recursion call-by-call and watch the call tree unfold, read a regex back in plain English before it bites you, or diagram your ideas on Scritch. Three tools, all in your browser, nothing uploaded.
Call tree● accepted
Scritch
Visualiser
Run JavaScript in a sandbox and watch the call tree unfold. Breakpoints, a step debugger, variables and a cost heatmap — built for learning recursion and DP.
OpenRex
Test a regex and watch the engine work: every attempt, every backtrack, the pattern as a diagram and in plain English — and whether it will hang on a long string.
OpenScritch
A quick whiteboard for diagrams, boxes and arrows — the kind of thing you'd draw on a whiteboard, or send your call tree straight to.
OpenPopular algorithm examples
Pick a classic problem and watch it run, step by step.