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| public class BinaryTreeZigzagLevelOrderTraversal {
public List<List<Integer>> zigzagLevelOrder(TreeNode root) {
List<List<Integer>> result = new ArrayList<List<Integer>>();
if (root == null) {
return result;
}
Queue<TreeNode> queue = new LinkedList<TreeNode>();
queue.add(root);
int crt, next;
crt = 1;
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.add(node.left);
next++;
}
if (node.right != null) {
queue.add(node.right);
next++;
}
if (crt == 0) {
crt = next;
next = 0;
result.add(new ArrayList<Integer>(list));
list.clear();
}
}
for (int i = 1; i < result.size(); i = i + 2) {
Collections.reverse(result.get(i));
}
return result;
}
}
|