91 lines
2.2 KiB
JavaScript
91 lines
2.2 KiB
JavaScript
class Digraph {
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arcs = new Map();
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addDependency(head, tail) {
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this.ensureTail(head);
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this.ensureTail(tail).add(head);
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}
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detectCycles() {
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const cycles = [];
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const visited = new Set();
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const walking = new Set();
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const walk = (vertex) => {
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if (!visited.has(vertex)) {
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visited.add(vertex);
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walking.add(vertex);
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const it = this.neighbors(vertex);
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for (let current = it.next(); true !== current.done; current = it.next()) {
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const {value: neighbor} = current;
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if (!visited.has(neighbor)) {
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walk(neighbor);
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}
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else if (walking.has(neighbor)) {
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cycles.push([vertex, neighbor]);
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}
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}
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}
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walking.delete(vertex);
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};
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const {tails} = this;
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for (let current = tails.next(); true !== current.done; current = tails.next()) {
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walk(current.value);
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}
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return cycles;
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}
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ensureTail(tail) {
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if (!this.arcs.has(tail)) {
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this.arcs.set(tail, new Set());
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}
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return this.arcs.get(tail);
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}
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neighbors(vertex) {
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return this.arcs.get(vertex).values();
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}
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sort() {
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const visited = new Set();
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const scores = new Map();
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const walk = (vertex, score) => {
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visited.add(vertex);
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const neighbors = this.neighbors(vertex);
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for (let current = neighbors.next(); true !== current.done; current = neighbors.next()) {
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const {value: neighbor} = current;
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if (!visited.has(neighbor)) {
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// eslint-disable-next-line no-param-reassign
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score = walk(neighbor, score);
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}
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}
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scores.set(vertex, score);
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return score - 1;
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};
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let score = this.arcs.size - 1;
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const {tails} = this;
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for (let current = tails.next(); true !== current.done; current = tails.next()) {
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const {value: vertex} = current;
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if (!visited.has(vertex)) {
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score = walk(vertex, score);
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}
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}
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return Array.from(scores.entries())
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.sort(([, l], [, r]) => l - r)
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.map(([vertex]) => vertex);
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}
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removeDependency(head, tail) {
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if (this.arcs.has(tail)) {
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this.arcs.get(tail).delete(head);
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}
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}
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get tails() {
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return this.arcs.keys();
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}
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}
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module.exports = Digraph;
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