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34 lines (30 loc) · 970 Bytes
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package leetcode.medium;
import java.util.ArrayList;
import java.util.Deque;
import java.util.LinkedList;
import java.util.List;
import utils.DataStructures.TreeNode;
public class P_102 {
public List<List<Integer>> levelOrder(TreeNode root) {
final List<List<Integer>> res = new ArrayList<>();
final Deque<TreeNode> dq = new LinkedList<>();
if (root != null) {
dq.offerFirst(root);
}
while (!dq.isEmpty()) {
final List<Integer> level = new ArrayList<>();
for (int size = dq.size(); size > 0; size--) {
final TreeNode curr = dq.removeLast();
level.add(curr.val);
if (curr.left != null) {
dq.offerFirst(curr.left);
}
if (curr.right != null) {
dq.offerFirst(curr.right);
}
}
res.add(level);
}
return res;
}
}