Tarjan的算法实现，低值节点问题

问题描述

我正在尝试从图中的一组节点上执行tarjans算法，我可以成功找到“强连接的组件”，但是根节点或低值节点始终处于关闭状态，即使对于只有1个元素的SCC来说，根节点也可以与该元素不匹配 例如：

0-3 IS LOW VALUE NODE
[82-97]
529-529 IS LOW VALUE NODE
[69-81]
379-379 IS LOW VALUE NODE
[57-68]
1619-1619 IS LOW VALUE NODE
[136-137]
415-415 IS LOW VALUE NODE
[45-56]

其中顶部是低值节点，底部是组成SCC的1个元素

我当前拥有的代码在这里

package Structs;

import java.util.*;

public class TarjanSCC {

    private int id;
    private boolean[] onStack;
    private int[] ids,low;
    private Deque<Integer> stack;
    private Graph<BasicBlock> graph;
    private Map<BasicBlock,Integer> nodeMap;
    private BasicBlock[] nodes;
    private static final int UNVISITED = -1;

    public TarjanSCC(Graph<BasicBlock> graph) {
        this.graph = graph;
    }

    public void runTSCC() {
        runTSCC(graph);
    }

    public void runTSCC(Graph<BasicBlock> nodeGraph) {

        //Initialize values for sorting
        this.nodes = nodeGraph.getNodes().toArray(new BasicBlock[nodeGraph.size()]);
        int size = nodes.length;
        this.ids = new int[size];
        this.low = new int[size];
        this.onStack = new boolean[size];
        this.stack = new arraydeque<>();
        this.nodeMap = new HashMap<>();

        //Mark all nodes as unused,place nodes in a map so index is easily retrievable from node
        for(int i = 0; i < size; i++) {
            nodeMap.put(nodes[i],i);
            ids[i] = UNVISITED;
        }

        //Invoke the DFS algorithm on each unvisited node
        for(int i = 0; i < size; i++) {
            if (ids[i] == UNVISITED) dfs(i,nodeGraph);
        }
    }

    private void dfs(int at,Graph<BasicBlock> nodeGraph) {
        ids[at] = low[at] = id++;
        stack.push(at);
        onStack[at] = true;

        //Visit All Neighbours of graph and mark as visited and add to stack,for (BasicBlock edge : nodeGraph.getEdges(nodes[at])) {
            int nodeArrayIndex = nodeMap.get(edge);
            if (ids[nodeArrayIndex] == UNVISITED) {
                dfs(nodeArrayIndex,nodeGraph);
                low[at] = Math.min(low[at],low[nodeArrayIndex]);
            }
            else if (onStack[nodeArrayIndex]) low[at] = Math.min(low[at],nodeArrayIndex);
        }

        //We've visited all the neighours,lets start emptying the stack until we're at the start of the SCC
        if (low[at] == ids[at]) {
            List<BasicBlock> scclist = new ArrayList<>();
            for (int node = stack.pop();; node = stack.pop()) {
                onStack[node] = false;
                scclist.add(0,nodes[node]);
                if (node == at) {
                    System.out.println(nodes[low[at]] + " IS LOW VALUE NODE");
                    System.out.println(scclist);
                    break;
                }
            }
        }
    }
}

我怀疑问题在于设置较低的值。 我认为不需要任何其他类信息，因为从图中检索边缘没有问题

解决方法

我索引根节点错误的节点[at]是访问根节点的正确方法