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68 lines
2.0 KiB
68 lines
2.0 KiB
/**
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* The Floyd–Warshall algorithm is an algorithm for finding shortest paths in
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* a weighted graph with positive or negative edge weights (but with no negative
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* cycles). - https://en.wikipedia.org/wiki/Floyd–Warshall_algorithm
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*/
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class FloydWarshall {
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/**
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* @ignore
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*/
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constructor() {
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}
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/**
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*
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* @param {Object} body
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* @param {Array.<Node>} nodesArray
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* @param {Array.<Edge>} edgesArray
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* @returns {{}}
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*/
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getDistances(body, nodesArray, edgesArray) {
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let D_matrix = {};
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let edges = body.edges;
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// prepare matrix with large numbers
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for (let i = 0; i < nodesArray.length; i++) {
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let node = nodesArray[i];
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let cell = {};
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D_matrix[node] = cell;
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for (let j = 0; j < nodesArray.length; j++) {
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cell[nodesArray[j]] = (i == j ? 0 : 1e9);
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}
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}
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// put the weights for the edges in. This assumes unidirectionality.
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for (let i = 0; i < edgesArray.length; i++) {
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let edge = edges[edgesArray[i]];
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// edge has to be connected if it counts to the distances. If it is connected to inner clusters it will crash so we also check if it is in the D_matrix
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if (edge.connected === true && D_matrix[edge.fromId] !== undefined && D_matrix[edge.toId] !== undefined) {
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D_matrix[edge.fromId][edge.toId] = 1;
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D_matrix[edge.toId][edge.fromId] = 1;
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}
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}
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let nodeCount = nodesArray.length;
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// Adapted FloydWarshall based on unidirectionality to greatly reduce complexity.
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for (let k = 0; k < nodeCount; k++) {
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let knode = nodesArray[k];
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let kcolm = D_matrix[knode];
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for (let i = 0; i < nodeCount - 1; i++) {
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let inode = nodesArray[i];
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let icolm = D_matrix[inode];
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for (let j = i + 1; j < nodeCount; j++) {
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let jnode = nodesArray[j];
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let jcolm = D_matrix[jnode];
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let val = Math.min(icolm[jnode], icolm[knode] + kcolm[jnode]);
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icolm[jnode] = val;
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jcolm[inode] = val;
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}
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}
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}
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return D_matrix;
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}
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}
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export default FloydWarshall;
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