@antv/algorithm
Version:
graph algorithm
123 lines • 4.06 kB
JavaScript
import { getNeighbors } from "./util";
/**
* Generate all connected components for an undirected graph
* @param graph
*/
export var detectConnectedComponents = function detectConnectedComponents(graphData) {
var _a = graphData.nodes,
nodes = _a === void 0 ? [] : _a,
_b = graphData.edges,
edges = _b === void 0 ? [] : _b;
var allComponents = [];
var visited = {};
var nodeStack = [];
var getComponent = function getComponent(node) {
nodeStack.push(node);
visited[node.id] = true;
var neighbors = getNeighbors(node.id, edges);
var _loop_1 = function _loop_1(i) {
var neighbor = neighbors[i];
if (!visited[neighbor]) {
var targetNode = nodes.filter(function (node) {
return node.id === neighbor;
});
if (targetNode.length > 0) {
getComponent(targetNode[0]);
}
}
};
for (var i = 0; i < neighbors.length; ++i) {
_loop_1(i);
}
};
for (var i = 0; i < nodes.length; i++) {
var node = nodes[i];
if (!visited[node.id]) {
// 对于无向图进行dfs遍历，每一次调用后都得到一个连通分量
getComponent(node);
var component = [];
while (nodeStack.length > 0) {
component.push(nodeStack.pop());
}
allComponents.push(component);
}
}
return allComponents;
};
/**
* Tarjan's Algorithm 复杂度 O(|V|+|E|)
* For directed graph only
* a directed graph is said to be strongly connected if "every vertex is reachable from every other vertex".
* refer: http://en.wikipedia.org/wiki/Tarjan%27s_strongly_connected_components_algorithm
* @param graph
* @return a list of strongly connected components
*/
export var detectStrongConnectComponents = function detectStrongConnectComponents(graphData) {
var _a = graphData.nodes,
nodes = _a === void 0 ? [] : _a,
_b = graphData.edges,
edges = _b === void 0 ? [] : _b;
var nodeStack = [];
var inStack = {}; // 辅助判断是否已经在stack中，减少查找开销
var indices = {};
var lowLink = {};
var allComponents = [];
var index = 0;
var getComponent = function getComponent(node) {
// Set the depth index for v to the smallest unused index
indices[node.id] = index;
lowLink[node.id] = index;
index += 1;
nodeStack.push(node);
inStack[node.id] = true;
// 考虑每个邻接点
var neighbors = getNeighbors(node.id, edges, 'target').filter(function (n) {
return nodes.map(function (node) {
return node.id;
}).indexOf(n) > -1;
});
var _loop_2 = function _loop_2(i) {
var targetNodeID = neighbors[i];
if (!indices[targetNodeID] && indices[targetNodeID] !== 0) {
var targetNode = nodes.filter(function (node) {
return node.id === targetNodeID;
});
if (targetNode.length > 0) {
getComponent(targetNode[0]);
}
// tree edge
lowLink[node.id] = Math.min(lowLink[node.id], lowLink[targetNodeID]);
} else if (inStack[targetNodeID]) {
// back edge, target node is in the current SCC
lowLink[node.id] = Math.min(lowLink[node.id], indices[targetNodeID]);
}
};
for (var i = 0; i < neighbors.length; i++) {
_loop_2(i);
}
// If node is a root node, generate an SCC
if (lowLink[node.id] === indices[node.id]) {
var component = [];
while (nodeStack.length > 0) {
var tmpNode = nodeStack.pop();
inStack[tmpNode.id] = false;
component.push(tmpNode);
if (tmpNode === node) break;
}
if (component.length > 0) {
allComponents.push(component);
}
}
};
for (var _i = 0, nodes_1 = nodes; _i < nodes_1.length; _i++) {
var node = nodes_1[_i];
if (!indices[node.id] && indices[node.id] !== 0) {
getComponent(node);
}
}
return allComponents;
};
export default function getConnectedComponents(graphData, directed) {
if (directed) return detectStrongConnectComponents(graphData);
return detectConnectedComponents(graphData);
}