arraylist的Arraylists作为关系的代表

Question

I have several values, like this: (Elements in a row are in relationship.)

       Vertex relationships(edges)
    Source vertex   Destination vertex

    x1 26   y1 287   x2 154   y2 303
    x1 22   y1 114   x2 115   y2 185
    x1 26   y1 287   x2 375   y2 338
    x1 26   y1 287   x2 260   y2 393
    x1 115  y1 185   x2 121   y2 7
    x1 200  y1 101   x2 392   y2 238
    x1 99   y1 394   x2 375   y2 338
    x1 99   y1 394   x2 121   y2 7
    x1 274  y1 28    x2 22    y2 114
    x1 296  y1 185   x2 200   y2 101
    x1 115  y1 185   x2 154   y2 303

I should find all the values which are in relationship and put them into a list, like this: [26,287 154,303 375,338 260,393] I have tried to use this code:

    for (int i=0; i<vertexnum; i++) {
        adjLists.add(new ArrayList<Integer>());
    }

    for (int j=0; j<vertexnum; j++) {
        for (Point p : nodes) {
            for (Edge e : edges) {
                adjLists.get(j).add(e.p1.x);
                adjLists.get(j).add(e.p1.y);
                adjLists.get(j).add(0);

                adjLists.get(j).add(e.p2.x);
                adjLists.get(j).add(e.p2.y);
                adjLists.get(j).add(0);
                for (Point p1 : nodes) {
                    for (Edge e1 : edges) {
                        if (e1.p1.x == e.p1.x && e1.p1.y == e.p1.y && !adjLists.get(j).contains(e1.p2.x) && !adjLists.get(j).contains(e1.p2.y)) {
                            adjLists.get(j).add(e1.p2.x);
                            adjLists.get(j).add(e1.p2.y);
                            adjLists.get(j).add(0);
                        } else if(e1.p2.x == e.p1.x && e1.p2.y == e.p1.y && !adjLists.contains(e1.p1.x) && !adjLists.contains(e1.p1.y)){
                            adjLists.get(j).add(e1.p1.x);
                            adjLists.get(j).add(e1.p1.y);
                            adjLists.get(j).add(0);
                        }
                    }
                }
            }
        }
    }

It creates only one ArrayList, it gives all elements in a row instead of separately. I have tried debugging, but I can not see what causes this.

Example of what I want:

Answer 1

I'll take this in three steps: define the data structures, define the problem, provide a solution.

Define the Data Structures

• Vertex: in your example a vertex seems to be a unique pair of integers. Point should be a pretty good fit
• Relationship: This seems to be an edge defined by two Vertexes. You should write a simple pojo for this, but for the sake of brevity we'll use Pair from apache commons. Lets declare that the Relationships go from right to left. Thus Pair<Point, Point> relationship = new ImmutablePair<Point, Point>(new Point(26, 287), new Point(154, 303)); is equivalent to the first line in your example data.

Define the Problem

You want a method that takes in a list of Relationships and spits out a list of lists showing where one can get to from any given Vertex. I'll take it one further and return map with from points as keys and sets of possible to points as values. ie. Map<Point,Set<Point>>

Solution

At this point the background is clearly defined and finding a solution is easy

public static Map<Point, Set<Point>> createTraversalMap(List<Pair<Point, Point>> relationshipList) {
    Map<Point, Set<Point>> traversalMap = new HashMap<Point, Set<Point>>();
    for (Pair<Point, Point> relationship : relationshipList) {
        Point fromVertex = relationship.getLeft(), toVertex = relationship.getRight();
        Set<Point> toSet = traversalMap.get(fromVertex);// set of Vertexes we've found so far for the current "from" Vertex
        if (toSet == null) {// bootstrap the set
            toSet = new HashSet<Point>();
            traversalMap.put(fromVertex, toSet);
        }
        toSet.add(toVertex);
        // traversalMap.put(fromVertex, toSet); //not needed, but good to keep in mind
    }
    return traversalMap;
}

Note, I have not tested this in any way