二叉树中序遍历

public class T94 {
    public List<Integer> inorderTraversal(TreeNode root) {
        Stack<TreeNode> stack = new Stack<>();
        List<Integer> list = new ArrayList<>();
        TreeNode tempRoot = root;
        while (tempRoot != null || !stack.isEmpty()) {
            while (tempRoot != null) {
                stack.push(tempRoot);
                tempRoot = tempRoot.left;
            }
            //root左为空
            TreeNode node = stack.pop();
            list.add(node.val);
            tempRoot = node.right;
        }
        return list;
    }
}