Question

我试图用Java编写一个广度优先搜索的实现（不完整）但是当我尝试迭代所有相邻顶点到起始顶点时，我遇到了一个问题。

程序正在迭代所有相邻的顶点，但是当它到达if语句时，它检查是否已经访问过TargetVertex，它总是返回true而不是false，因此永远不会在括号内运行代码。

我不确定为什么会发生这种情况，因为在Vertex类中我已将所有新顶点的visited值初始化为false。有没有人看到我犯的错误或知道为什么会发生这种错误？我已经查看了所有其他方法/类，并且在任何时候都没有改变＆＃34; visit＆＃34;的值。任何帮助，将不胜感激！！

public void doBFS(String s){

    //Create a queue
    Queue<Vertex> q = new LinkedList<Vertex>();

    //Create an arraylist to keep track of visited vertices
    ArrayList<String> visited = new ArrayList<String>();

    // Retrieve the starting vertex u, using the string name entered
    Vertex u = vertices.get(s);

   //Enqueue the starting node and add it to the visited set
   visited.add(u.name);
   u.visited = true;
   u.distance = 0;
   q.add(u);


 while (! q.isEmpty() ) {

   Vertex current = q.remove();

       for (Edge e : current.getEdges()) {
          //HERE IS THE PROBLEM. It always says it's true.
        if(e.targetVertex.visited = false) {

            visited.add(e.targetVertex.name);
            q.add(e.targetVertex);
            e.targetVertex.visited=true;        
        } 

        current = e.targetVertex;  
   }

}

}

我的Vertex类的开头：

 public class Vertex {
   public String name;
   private List<Edge> adjacent;
   public int posX = 0;
   public int posY = 0;
   public boolean visited = false;
   public double distance = Double.POSITIVE_INFINITY;

   /**
   * Construct a new vertex containing an adjacency list.
   * 
   * @param vertexName
   *          a unique identifier for this vertex.
   * @param x
   *          the x coordinate for this vertex
   * @param y
   *          the y coordinate for this vertex
   */
  public Vertex(String vertexName, int x, int y) {
    name = vertexName;
    adjacent = new LinkedList<Edge>();
    posX = x;
    posY = y;
    distance = Double.POSITIVE_INFINITY; 
    visited = false;
  }

Answer 1

if(e.targetVertex.visited = false) {

...是一项任务。使用

    if(e.targetVertex.visited == false) {

......或者只是

if(!e.targetVertex.visited) {

为什么以下语句返回true？

1 个答案: