判断是不是平衡二叉树

    static int flag=0;
    public boolean isBalanced(TreeNode root) {
        flag=0;
        travel12(root);
        if(flag==1){
            return false;
        } else {
            return true;
        }
    }

    public int travel12(TreeNode node){
        if(node==null){
            return 0;
        }
        int hl=travel12(node.left)+1;
        int hr=travel12(node.right)+1;
        if(hl-hr>1||hr-hl>1){
            flag=1;
        }
        return hl>hr?hl:hr;
    }