文章目录
题目描述
做题思路
代码实现
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode() {}
* TreeNode(int val) { this.val = val; }
* TreeNode(int val, TreeNode left, TreeNode right) {
* this.val = val;
* this.left = left;
* this.right = right;
* }
* }
*/
class Solution {
public List<List<Integer>> zigzagLevelOrder(TreeNode root) {
List<List<Integer>> res=new ArrayList<>();
if(root==null)return res;
Deque<TreeNode>[] stack=new Deque[2];
for(int i=0;i<2;i++){
stack[i]=new ArrayDeque<TreeNode>();
}
stack[1].push(root);
int flag=1;
while(!stack[flag].isEmpty()){
List<Integer> tem=new ArrayList<>();
int size=stack[flag].size();
for(int i=0;i<size;i++){
TreeNode head=stack[flag].pop();
if(flag==1){
if(head.left!=null){
stack[0].push(head.left);
}
if(head.right!=null){
stack[0].push(head.right);
}
}
if(flag==0){
if(head.right!=null){
stack[1].push(head.right);
}
if(head.left!=null){
stack[1].push(head.left);
}
}
tem.add(head.val);
}
res.add(tem);
flag=(flag+1)%2;
}
return res;
}
}
题目链接
103. 二叉树的锯齿形层序遍历
