leetcode110_平衡二叉树

class Solution {
    public boolean isBalanced(TreeNode root) {
        if(root == null) return true;
        return getHeight(root)== -1 ? false : true;
    }
    private int getHeight(TreeNode root) {
        if(root == null) return 0;
        int leftHeight = getHeight(root.left);
        if(leftHeight == -1) return -1;
        int rightHeight = getHeight(root.right);
        if(rightHeight == -1) return -1;
        if(Math.abs(leftHeight - rightHeight) > 1) return -1;
        else return Math.max(leftHeight, rightHeight) + 1;
    }
}