[英]Return number of edges of each vertex in a digraph (jgrapht)
我有使用以下方法創建的有向圖:
public static DirectedGraph<Point, DefaultEdge> directedGraph = new DefaultDirectedGraph<Point, DefaultEdge>(DefaultEdge.class);
void setup() {
Point myPoint = new Point(x, y);
Point myNextPoint = new Point(xToFillNext, yToFillNext);
directedGraph.addVertex(myPoint);
directedGraph.addVertex(myNextPoint);
directedGraph.addEdge(myPoint, myNextPoint);
Point mySecondPoint = new Point(x, y);
Point mySecondNextPoint = new Point(xToFillNext, yToFillNext);
directedGraph.addVertex(mySecondPoint);
directedGraph.addVertex(mySecondNextPoint);
directedGraph.addEdge(mySecondPoint, mySecondNextPoint);
System.out.println("#vertices: "+ directedGraph.vertexSet());
}
public static class Point {
public int x;
public int y;
public Point(int x, int y)
{
this.x = x;
this.y = y;
}
@Override
public String toString() {
return ("[x="+x+" y="+y+"]");
}
@Override
public int hashCode() {
int hash = 7;
hash = 71 * hash + this.x;
hash = 71 * hash + this.y;
return hash;
}
@Override
public boolean equals(Object other)
{
if (this == other)
return true;
if (!(other instanceof Point))
return false;
Point otherPoint = (Point) other;
return otherPoint.x == x && otherPoint.y == y;
}
}
我想使用以下方法獲取每個頂點的向外邊緣數量:
directedGraph.outDegreeOf()
但是我不想逐個頂點地進行操作(這是一個簡單的代碼,可以更輕松地進行遍歷,在我的整個程序中,我有更多的頂點),我想遍歷頂點集並返回無論有多少個頂點,集合中每個頂點的向外邊緣的數量都會自動增加。
我應該如何進行呢?
(我使用基於Java的處理)
查看JGrapht API 。
DirectedGraph
接口包含一個vertexSet()
函數。 您可以使用它來迭代添加的頂點,並且可以獲得每個頂點的outDegreeValue()
:
for(Point p : directedGraph.vertexSet()){
int degree = directedGraph.outDegreeOf(p);
System.out.println("Degree of " p.toString() + ": " + degree);
}
我不確定DirectedGraph
是否固有地存儲此信息,但是您可以通過使用hasmap在添加邊的同時輕松存儲此信息。
HashMap<Integer,Integer> outEdgesMap = new HashMap<Integer,Integer>();
你在做
directedGraph.addEdge(myPoint, myNextPoint);
在這之后也做
outEdgesMap.put(myPoint,outEdgesMap.getOrDefault(myPoint,0)+1);
只是要清楚,它將是
directedGraph.addEdge(myPoint, myNextPoint);
outEdgesMap.put(myPoint,outEdgesMap.getOrDefault(myPoint,0)+1);
所以你的directedGraph.outDegreeOf()
將是
for(Integer i : outEdgesMap.keySet()){
sout(i+ " : " +outEdgesMap.get(i) );
}
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