Leetcode Q94 二叉树的中序遍历
public void inorder(TreeNode root){
List<Integer> res = new ArrayList<>();
TreeNode cur = root;
Deque<TreeNode> stack = new LinkedList<>();
while(cur!=null || !stack.isEmpty()){
while(cur!=null){
stack.add(cur);
cur = cur.left;
}
cur = stack.removeLast();
res.add(cur.val);
cur = cur.right;
}
}