返回节点列表 Java-Parent 中的树可以有多个子节点
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Return list of Nodes a Tree in Java-Parent can have multiple child Nodes
提问by crazyTechie
I am trying to write java code to return list of Nodes in a tree.
The tree looks like 
我正在尝试编写 java 代码来返回树中的节点列表。这棵树看起来像
Node class is
节点类是
class Node{
String label;
List<Node> children;
}
I am trying this way. But not able to understand how to write a loop to traverse.
我正在尝试这种方式。但无法理解如何编写循环来遍历。
public List<Node> returnAllNodes(Node node){
List<Node> listOfNodes =
new ArrayList<Node>();
boolean iterationCompleted = false;
if(node==null){
return null;
}
while(!iterationCompleted){
if(node.getChildren()==null){
listOfNodes.add(node);
break;
}
else{
//
}
}
return null;
//return traverseAndReturnAllNodes(node.getChildren().get(0));
}
Please help.
请帮忙。
回答by Maurice Perry
If you're certain that the structure is a tree (a node cannot have more than one parent), this will list the nodes in depth-first order:
如果您确定该结构是一棵树（一个节点不能有多个父节点），这将按深度优先顺序列出节点：
public static List<Node> returnAllNodes(Node node){
List<Node> listOfNodes = new ArrayList<Node>();
addAllNodes(node, listOfNodes);
return listOfNodes;
}
private static void addAllNodes(Node node, List<Node> listOfNodes) {
if (node != null) {
listOfNodes.add(node);
List<Node> children = node.getChildren();
if (children != null) {
for (Node child: children) {
addAllNodes(child, listOfNodes);
}
}
}
}
If nodes can have several parents, change the first line of addAllNodes to:
如果节点可以有多个父节点，请将 addAllNodes 的第一行更改为：
if (node != null && !listOfNodes.contains(node)) {
The breadth-first algorithm goes like this:
广度优先算法是这样的：
public static List<Node> returnAllNodes(Node node){
List<Node> listOfNodes = new ArrayList<Node>();
if (node != null) {
listOfNodes.add(node);
for(int i = 0; i < listOfNodes.size(); ++i) {
Node n = listOfNodes.get(i);
List<Node> children = n.getChildren();
if (children != null) {
for (Node child: children) {
if (!listOfNodes.contains(child)) {
listOfNodes.add(child);
}
}
}
}
}
return listOfNodes;
}
回答by npclaudiu
You can use Breadth-first searchor Depth-first search.
