87 lines
2.0 KiB
JavaScript
87 lines
2.0 KiB
JavaScript
var _ = require("./lodash");
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module.exports = parentDummyChains;
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function parentDummyChains(g) {
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var postorderNums = postorder(g);
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_.forEach(g.graph().dummyChains, function(v) {
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var node = g.node(v);
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var edgeObj = node.edgeObj;
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var pathData = findPath(g, postorderNums, edgeObj.v, edgeObj.w);
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var path = pathData.path;
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var lca = pathData.lca;
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var pathIdx = 0;
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var pathV = path[pathIdx];
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var ascending = true;
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while (v !== edgeObj.w) {
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node = g.node(v);
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if (ascending) {
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while ((pathV = path[pathIdx]) !== lca &&
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g.node(pathV).maxRank < node.rank) {
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pathIdx++;
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}
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if (pathV === lca) {
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ascending = false;
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}
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}
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if (!ascending) {
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while (pathIdx < path.length - 1 &&
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g.node(pathV = path[pathIdx + 1]).minRank <= node.rank) {
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pathIdx++;
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}
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pathV = path[pathIdx];
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}
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g.setParent(v, pathV);
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v = g.successors(v)[0];
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}
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});
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}
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// Find a path from v to w through the lowest common ancestor (LCA). Return the
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// full path and the LCA.
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function findPath(g, postorderNums, v, w) {
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var vPath = [];
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var wPath = [];
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var low = Math.min(postorderNums[v].low, postorderNums[w].low);
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var lim = Math.max(postorderNums[v].lim, postorderNums[w].lim);
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var parent;
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var lca;
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// Traverse up from v to find the LCA
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parent = v;
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do {
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parent = g.parent(parent);
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vPath.push(parent);
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} while (parent &&
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(postorderNums[parent].low > low || lim > postorderNums[parent].lim));
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lca = parent;
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// Traverse from w to LCA
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parent = w;
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while ((parent = g.parent(parent)) !== lca) {
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wPath.push(parent);
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}
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return { path: vPath.concat(wPath.reverse()), lca: lca };
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}
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function postorder(g) {
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var result = {};
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var lim = 0;
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function dfs(v) {
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var low = lim;
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_.forEach(g.children(v), dfs);
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result[v] = { low: low, lim: lim++ };
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}
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_.forEach(g.children(), dfs);
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return result;
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}
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