【LeetCode】C# 110、Balanced Binary Tree

Given a binary tree, determine if it is height-balanced.

For this problem, a height-balanced binary tree is defined as a binary tree in which the depth of the two subtrees of every node never differ by more than 1.

题意：给定二叉树并判定其是否为高度平衡的二叉树。
思路：高度平衡二叉树的定义：其左右子树均为高度平衡的二叉树，而且其左右子树的高度差小于1。可以递归。每次递归时，当自身为高度平衡，则返回自身高度。否则返回负数。每个递归利用下次递归返回的高度，即其左右子树的高度，来判断自身其是否合格。是则返回高度，否则返回负数。

/** * Definition for a binary tree node. * public class TreeNode { *     public int val; *     public TreeNode left; *     public TreeNode right; *     public TreeNode(int x) { val = x; } * } */public class Solution {    public bool IsBalanced(TreeNode root) {        if(root==null){            return true;        }        return height(root)!=-1;    }    public int height(TreeNode node){        if(node==null){            return 0;        }        int lH=height(node.left);        if(lH==-1){            return -1;        }        int rH=height(node.right);        if(rH==-1){            return -1;        }        if(lH-rH<-1 || lH-rH>1){            return -1;        }        return Math.Max(lH,rH)+1;    }}