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| public class BinaryTreeLevelOrderTraversal {
public List<List<Integer>> levelOrder(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 crt = 1;
int next = 0;
List<Integer> list = new ArrayList<Integer>();
while (!queue.isEmpty()) {
TreeNode node = queue.poll();
list.add(node.val);
crt--;
if (node.left != null) {
queue.offer(node.left);
next++;
}
if (node.right != null) {
queue.offer(node.right);
next++;
}
if (crt == 0) {
result.add(new ArrayList<Integer>(list));
list.clear();
crt = next;
next = 0;
}
}
return result;
}
@Test
public void test() {
TreeNode root = new TreeNode(1);
root.left = new TreeNode(2);
List<List<Integer>> result = levelOrder(root);
}
}
|