题目
https://leetcode-cn.com/problems/cong-shang-dao-xia-da-yin-er-cha-shu-iii-lcof
解法
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| class Solution {
public List<List<Integer>> levelOrder(TreeNode root) {
Queue<TreeNode> queue = new LinkedList<>();
List<List<Integer>> res = new ArrayList<>();
boolean flag = true;
if (root != null) queue.add(root);
while (!queue.isEmpty()) {
List<Integer> list = new ArrayList<>();
for (int i= queue.size(); i>0; i--) {
TreeNode node = queue.poll();
list.add(node.val);
if (node.left != null) queue.add(node.left);
if (node.right != null) queue.add(node.right);
}
if(!flag)
list = reverse(list);
flag = !flag;
res.add(list);
}
return res;
}
public List<Integer> reverse(List<Integer> list){
List<Integer> res = new ArrayList<>();
for(int i = list.size()-1; i >= 0; i --){
res.add(list.get(i));
}
return res;
}
}
|
