题目描述
请实现一个函数按照之字形打印二叉树,即第一行按照从左到右的顺序打印,第二层按照从右至左的顺序打印,第三行按照从左到右的顺序打印,其他行以此类推。
import java.util.ArrayList;
/*
public class TreeNode {
int val = 0;
TreeNode left = null;
TreeNode right = null;
public TreeNode(int val) {
this.val = val;
}
}
*/
import java.util.*;
public class Solution {
ArrayList<ArrayList<Integer> > Print(TreeNode pRoot) {
ArrayList<ArrayList<Integer> > ans = new ArrayList();
List<Integer > list = new ArrayList();
Queue<TreeNode> queue = new LinkedList();
TreeNode node;
queue.add(pRoot);
int count = 1;
int temp = 0;
int num = 0;
if(pRoot == null) return ans;
while (!queue.isEmpty()){
node = queue.poll();
if (node.left != null) {
queue.add(node.left);
temp++;
}
if (node.right != null) {
queue.add(node.right);
temp++;
}
list.add(node.val);
count--;
if (count == 0) {
num++;
if(num%2 == 0){
Collections.reverse(list);
}
ans.add(new ArrayList<>(list));
list.clear();
count = temp;
temp = 0;
}
}
return ans;
}
}