判断一棵树是否是平衡二叉树

package 判断一棵树是否是平衡二叉树;

class TreeNode {
int val = 0;
TreeNode left = null;
TreeNode right = null;

public TreeNode(int val) {
this.val = val;

}
}

public class Solution {
public boolean IsBalanced_Solution(TreeNode root) {
if (root == null) {
return true;
}
boolean[] res = new boolean[1];
res[0] = true;
depth(root, 1, res);
return res[0];
}

private int depth(TreeNode root, int acc, boolean res[]) {
int leftHeight, rightHeight;
if (root.left != null) {
leftHeight = depth(root.left, acc + 1, res);
} else {
leftHeight = acc;
}
if (root.right != null) {
rightHeight = depth(root.right, acc + 1, res);
} else {
rightHeight = acc;
}
if(Math.abs(leftHeight-rightHeight)>1){
res[0] = false;
}
return Math.max(leftHeight, rightHeight);
}

public static void main(String[] args) {
TreeNode root = new TreeNode(1);
TreeNode left1 = new TreeNode(1);
TreeNode left2 = new TreeNode(1);
root.left = left1;
left1.left = left2;
System.out.println(new Solution().IsBalanced_Solution(root));
}
}