树遍历

public List<Integer> inorderTraversal(TreeNode root) {
    List<Integer> list = new ArrayList<Integer>();

    Stack<TreeNode> stack = new Stack<TreeNode>();
    TreeNode cur = root;

    while(cur!=null || !stack.empty()){
        while(cur!=null){
            stack.add(cur);
            cur = cur.left;
        }
        cur = stack.pop();
        list.add(cur.val);
        cur = cur.right;
    }

    return list;
}

 

先往左走到最底，利用stack慢慢把堆里面的节点抛出来处理，内层的while中处理左节点，内层的非while抛出右边节点处理