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