Algorithms—110.Balanced Binary Tree

思路：比较左树和右树的深度，如果相差不超过1，继续判断左树和右树是否为平衡树。

/**
* 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 (Math.abs(f(root.left)-f(root.right))>1) {
return false;
}
return isBalanced(root.left)&&isBalanced(root.right);
}
public int f(TreeNode root){
if (root==null) {
return 0;
}else {
return 1+Math.max(f(root.left), f(root.right));
}
}
}