76 lines
2.1 KiB
JavaScript
76 lines
2.1 KiB
JavaScript
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(function (exports) {
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'use strict';
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/**
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* Tarjan's algorithm for finding the connected components in a graph.<br><br>
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* Time complexity: O(|E| + |V|) where E is a number of edges and |V|
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* is the number of nodes.
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*
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* @public
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* @module graphs/others/tarjan-connected-components
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* @param {Array} graph Adjacency list, which represents the graph.
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* @returns {Array} Connected components.
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*
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* @example
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* var tarjanConnectedComponents =
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* require('path-to-algorithms/src/graphs/' +
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* 'others/tarjan-connected-components').tarjanConnectedComponents;
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* var graph = {
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* v1: ['v2', 'v5'],
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* v2: [],
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* v3: ['v1', 'v2', 'v4', 'v5'],
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* v4: [],
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* v5: []
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* };
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* var vertices = topsort(graph); // ['v3', 'v4', 'v1', 'v5', 'v2']
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*/
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function tarjanConnectedComponents(graph) {
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graph = graph || {};
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const indexes = {};
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const lowIndexes = {};
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const onStack = {};
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const result = [];
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const stack = [];
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var index = 1;
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const connectedComponent = function (node) {
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stack.push(node);
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onStack[node] = true;
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indexes[node] = index;
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lowIndexes[node] = index;
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index += 1;
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graph[node].forEach(function (n) {
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if (indexes[n] === undefined) {
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connectedComponent(n);
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lowIndexes[node] = Math.min(lowIndexes[n], lowIndexes[node]);
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} else if (onStack[n]) {
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lowIndexes[node] = Math.min(lowIndexes[node], indexes[n]);
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}
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});
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// This is a "root" node
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const cc = [];
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if (indexes[node] === lowIndexes[node]) {
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var current;
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do {
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current = stack.pop();
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onStack[current] = false;
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cc.push(current);
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} while (stack.length > 0 && node !== current);
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result.push(cc);
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}
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};
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Object.keys(graph)
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.forEach(function (n) {
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if (!indexes[n]) {
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connectedComponent(n);
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}
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});
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return result;
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}
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exports.tarjanConnectedComponents = tarjanConnectedComponents;
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}(typeof exports === 'undefined' ? window : exports));
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