import java.util.LinkedList;
import java.util.List;
public class PathSumII {
public List> pathSum(TreeNode root, int sum) {
List> result = new LinkedList<>();
pathSum(root, sum, result, new LinkedList());
return result;
}
/**
* 这里一定要拷贝一份链表再加到result
* 此时path中已经包含了root，sum中还不包含root
*/
private void pathSum(TreeNode root, int sum, List> result, List list) {
if (root == null) {
return;
}
list.add(root.val);
if (root.left == null && root.right == null && sum == root.val) {
result.add(new LinkedList<>(list));
return;
}
if (root.left != null) {
pathSum(root.left, sum - root.val, result, list);
list.remove(list.size() - 1);
}
if (root.right != null) {
pathSum(root.right, sum - root.val, result, list);
list.remove(list.size() - 1);
}
}
}