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| public class BinaryTreeLevelOrderTraversalII {
public List<List<Integer>> levelOrderBottom(TreeNode root) {
List<List<Integer>> result = new ArrayList<List<Integer>>();
if (root == null) {
return result;
}
Queue<TreeNode> queue = new LinkedList<TreeNode>();
queue.offer(root);
int c1 = 1;
int c2 = 0;
List<Integer> crt = new ArrayList<Integer>();
while (!queue.isEmpty()) {
TreeNode node = queue.poll();
crt.add(node.val);
c1--;
if (node.left != null) {
queue.offer(node.left);
c2++;
}
if (node.right != null) {
queue.offer(node.right);
c2++;
}
if (c1 == 0) {
c1 = c2;
c2 = 0;
result.add(0, new ArrayList<Integer>(crt));
crt.clear();
}
}
if (!crt.isEmpty()) {
result.add(0, new ArrayList<Integer>(crt));
}
return result;
}
}
|