Balanced Binary Tree ----- LeetCode

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.

解题思路： 平衡二叉树的左右子树的高度差不大于1, 对于每棵子树的左右子树高度差也都不大于1。

           使用递归遍历二叉树，计算每个节点的左右子树高度差，高度差大于1则返回-1，否则返回该节点的高度。

/**
 * Definition for binary tree
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
   public int searchHeight(TreeNode root){
    if(root==null){
    return 0;
    }            
    int left=searchHeight(root.left);
    int right=searchHeight(root.right);        
         if(left==-1||right==-1){
        return -1;
         }
         int height=Math.abs(left-right);
         if(height>1){
        return -1;
         }     
    return Math.max(left,right)+1;    
   }

   public boolean isBalanced(TreeNode root) {        
         return searchHeight(root)!=-1;        
   }
}