如何快速的检测cycle，对于无向边

GSQL 图算法库
#1

如何快速的检测cycle，对于无向边？

#2

请参考一下https://docs.tigergraph.com/dev/gsql-examples/classic-graph-algorithms#2-unidirectional-bfs-algorithm的案例，代码如下：

/**
 * This query assumes every edge in the graph is undirected.
 * It uses breadth-first-search to find the shortest path between s and t.
 */
// 1 May 2018: v2.0 - ListAccum "+" behavior changed.  Need to use FOREACH.

CREATE QUERY shortest_path_1D (VERTEX<company> S, VERTEX<company> T, INT maxDepth) FOR GRAPH work_graph{
  
  OrAccum @@found  = false;
  OrAccum @notSeen = true;
  ListAccum<STRING>  @pathResult; 
  Start (ANY) = {S};
  Start = SELECT v
    FROM Start:v
    //assume each vertex has an id attribute
    ACCUM v.@notSeen = false, v.@pathResult = v.id;
  
  WHILE NOT @@found LIMIT maxDepth DO
    Start = SELECT v
      FROM Start - (:e) -> :v
      WHERE v.@notSeen
      ACCUM v.@notSeen = false,
            //add partial result paths to target v. v2.0 ListAccum requires FOREACH.
            FOREACH path IN Start.@pathResult DO
                v.@pathResult += (path + "-" + v.id)
            END,
            CASE WHEN v == T
              THEN @@found += true
            END;
  END;
  
  IF @@found THEN
    Result = {T};
    #PRINT Result.@pathResult;         #JSON output API version v1
    PRINT Result [Result.@pathResult]; #JSON output API version v2
  ELSE 
    PRINT "Can't find shortest path within max steps";
  END;
}
INSTALL QUERY shortest_path_1D

该案例中通过OrAccum @notSeen 来确定不会走环路。

关于无向边的SetAccum