Open larscheng opened 3 months ago
广度优先遍历
class Solution {
//O(n)/O(n)
public List<List<Integer>> levelOrder(TreeNode root) {
if (root==null){
return new ArrayList<>();
}
List<List<Integer>> res = new ArrayList<>();
Deque<TreeNode> queue = new ArrayDeque<>();
queue.add(root);
while (!queue.isEmpty()){
List<Integer> temp = new ArrayList<>();
int size = queue.size();
for (int i = 0; i < size; i++) {
TreeNode node = queue.poll();
temp.add(node.val);
if (node.left!=null){
queue.add(node.left);
}
if (node.right!=null){
queue.add(node.right);
}
}
res.add(temp);
}
return res;
}
}
102. 二叉树的层序遍历