Graph Editor

Dragging, adding, or deleting on the canvas immediately rewrites the text box in whichever output format is selected above. Typing/pasting into the text box only takes effect once you click Apply text → canvas — it auto-detects algs4 vs. CS Academy markup (importing CS Academy markup also updates the Weighted/Directed toggles to match what it finds).

The Weighted/Directed toggles decide how a pasted algs4-format text is read back (2 vs. 3 numbers per edge line) and whether arrowheads are drawn — the underlying v w / v w weight text itself doesn't encode direction, exactly like the other pages: the same edge list works as input for an undirected page or a directed one.

Any coordinate scale works on import (CS Academy pixels, algs4's own 0…1 range, anything) — it's auto-centred and scaled to fit, preserving relative position and aspect ratio. Self-loops aren't supported by the canvas editor; parallel edges between the same pair are drawn as separate curved springs. Snap to grid rounds dragged/added positions to the nearest cell (size adjustable, shown as faint gridlines) — handy for tidy rows/columns; it has no effect while Spring preview is on, since dragging there only ever changes angle.

Mixed-format tolerant: in algs4 text, each edge occupies exactly one line. With Weighted on, a line missing its third number just defaults to weight 1; with it off, an extra third number is simply ignored — so pasting a graph doesn't need to match the toggle exactly, and the same edge list works whether you're feeding it to a weighted or unweighted page. Applying text also syncs the toggle to match what's actually there: if any edge line has a real weight, Weighted switches on (so that data isn't silently discarded); if none do, it switches off (so you don't end up with invented weight-1s on a graph that never had any).

Classroom workflow: build a graph here, name it under "Save as", click Download file, and move the downloaded .txt into a graphs/ folder next to these HTML pages on your webserver. Every page (including this editor's Load from graphs/ menu) will then offer it as an extra option alongside the built-in examples — either serve graphs/index.json (a JSON array of filenames, or {file, label} objects) as a manifest, or just enable directory listing on your static server (e.g. Python's python3 -m http.server does this by default) and skip the manifest entirely.