the-forest/client/node_modules/@rtsao/scc/index.js
2024-09-17 20:35:18 -04:00

52 lines
1.1 KiB
JavaScript

"use strict";
module.exports = tarjan;
// Adapted from https://en.wikipedia.org/wiki/Tarjan%27s_strongly_connected_components_algorithm#The_algorithm_in_pseudocode
function tarjan(graph) {
const indices = new Map();
const lowlinks = new Map();
const onStack = new Set();
const stack = [];
const scc = [];
let idx = 0;
function strongConnect(v) {
indices.set(v, idx);
lowlinks.set(v, idx);
idx++;
stack.push(v);
onStack.add(v);
const deps = graph.get(v);
for (const dep of deps) {
if (!indices.has(dep)) {
strongConnect(dep);
lowlinks.set(v, Math.min(lowlinks.get(v), lowlinks.get(dep)));
} else if (onStack.has(dep)) {
lowlinks.set(v, Math.min(lowlinks.get(v), indices.get(dep)));
}
}
if (lowlinks.get(v) === indices.get(v)) {
const vertices = new Set();
let w = null;
while (v !== w) {
w = stack.pop();
onStack.delete(w);
vertices.add(w);
}
scc.push(vertices);
}
}
for (const v of graph.keys()) {
if (!indices.has(v)) {
strongConnect(v);
}
}
return scc;
}