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.
代码如下：
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
public class Solution { public boolean isBalanced(TreeNode root) {
if(root==null)
return true; if(DFS(root)==-1)
return false; return true; } public int DFS(TreeNode root){
int left=1,right=1;
if(root.left!=null)
{
if(DFS(root.left)==-1)
return -1;
else
left=left+DFS(root.left);
}
if(root.right!=null)
{
if(DFS(root.right)==-1)
return -1;
else
right=right+DFS(root.right);
} if(left-right<-1||left-right>1)
return -1; return Math.max(left,right);
} }