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| class Solution {
public List<List<Integer>> BSTSequences(TreeNode root) {
List<List<Integer>> resultList = new ArrayList<>();
List<Integer> path = new ArrayList<>();
List<TreeNode> queue = new LinkedList<>();
if (root != null) {
queue.add(root);
}
bfs(resultList, path, queue);
return resultList;
}
private void bfs(List<List<Integer>> resultList, List<Integer> path, List<TreeNode> queue) {
if (queue.isEmpty()) {
resultList.add(new ArrayList<>(path));
}
for (int i = 0; i < queue.size(); i++) {
TreeNode node = queue.remove(i);
path.add(node.val);
if (node.left != null) {
queue.add(node.left);
}
if (node.right != null) {
queue.add(node.right);
}
bfs(resultList, path, queue);
if (node.right != null) {
queue.remove(queue.size() - 1);
}
if (node.left != null) {
queue.remove(queue.size() - 1);
}
path.remove(path.size() - 1);
queue.add(i, node);
}
}
}
|