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; } }