[bh-official]

Closes #11

Adds counting sort to the sorting visualizer at /algorithms/sorting/counting-sort.

What changed

• countingSort in src/lib/algorithms/sorting.js plus its SORTERS entry. It counts each value in a 100-slot array (one step per value, with v and count[v] shown as variables), then writes the values back in order (one step per write). Comparisons and swaps stay at 0 and writes end at n.
• A new "write" bar role (roles.js) so written slots do not look like shifts.
• Everything in the CONTRIBUTING checklist: code snippets in five languages, catalog page (insertion sort now links to it, removed from the planned list), explainer (includes when counting sort is a bad idea), comparison/learn copy, README table and roadmap, and three practice problems.
• The sorting overview grid is now 2 columns on medium screens and 4 on large, since there are four sorts.
• The "question only on the compare line" test now skips counting sort, because it has no comparisons and uses line 3 for i = 0.

Tests
New tests in tests/sorting.test.mjs: sorted output for random arrays, duplicates, single element, all equal, already sorted and reversed input; comparisons 0, swaps 0, writes == n; counting phase before write-back phase; no value lost or added. They failed before the change (no SORTERS.counting) and pass now.

Ran

• npm test: 127 pass, 0 fail (119 before)
• npm run lint: clean
• npm run build: succeeds, /algorithms/sorting/counting-sort is generated

Notes

• I built the page but did not look at it in a browser, so please check how the bars look, especially the new teal "Writing" colour.
• complexity.stable is "N/A": the visualizer rewrites plain numbers, so stability cannot be observed, and the explainer FAQ says why. Easy to change to "Yes" if you prefer the textbook label.
• The renderer is untouched. Counting steps reuse the key role while a value is read, the new write role for each write, and sorted for the filled prefix.

[vercel]

@bh-official is attempting to deploy a commit to the salsadsid's projects Team on Vercel.

A member of the Team first needs to authorize it.