Balanced Binary Tree

这几天A的都是二叉树的，如果输的基本操作掌握了，用递归很好解决这些题目的。这个可能不是最好的解法，明天再去Discuss看看有没有好的解法

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.

 

/**
 * Definition for binary tree
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    /**
     * 这里用递归实现
     * 如果为空节点返回true
     * 如果不为空比较左右子树的高度，如果高度差的绝对值小于等于1且左右子树都是平衡二叉树return true
     * @param root
     * @return
     */
    public boolean isBalanced(TreeNode root){
        if(null == root){
            return true;
        }else
        {
            return (Math.abs(getHeight(root.left) - getHeight(root.right)) <= 1) && isBalanced(root.left) && isBalanced(root.right);
        }
        
    }
    /**
     * 获取一棵树的高度
     * 递归获取
     * @param root
     * @return
     */
    public int getHeight(TreeNode root){
        if(null == root)
            return 0;
        else{
            int max = getHeight(root.left);
            if(max < getHeight(root.right))
            {
                max =getHeight(root.right);
            }
            return max + 1;
        }
    }
}