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Copy pathNPreOrderTreeObj.java
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52 lines (44 loc) · 1.14 KB
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package one_day_test;
import java.util.Collections;
import java.util.LinkedList;
import java.util.List;
/**
* 589. N叉树的前序遍历
* 给定一个 N 叉树，返回其节点值的前序遍历。
*
* 例如，给定一个 3叉树 :
* 返回其前序遍历: [1,3,5,6,2,4]。
*
*
*/
public class NPreOrderTreeObj {
public List<Integer> preorder(Node root) {
LinkedList<Node> stack = new LinkedList<>();
LinkedList<Integer> output = new LinkedList<>();
if (root == null) {
return output;
}
stack.add(root);
while (!stack.isEmpty()) {
Node node = stack.pollLast();
output.add(node.val);
Collections.reverse(node.children);
for (Node item : node.children) {
stack.add(item);
}
}
return output;
}
class Node {
public int val;
public List<Node> children;
public Node() {}
public Node(int _val) {
val = _val;
}
public Node(int _val, List<Node> _children) {
val = _val;
children = _children;
}
}
}