Java 二叉树深度 判断平衡二叉树

package cookie;

public class BTreeDepthIsBalanced {
    int depth(BNode head) {
        if (head == null) {
            return 0;
        }
        int left = depth(head.left);
        int right = depth(head.right);
        return left > right ? left + 1 : right + 1;
    }

    boolean isBalanced(BNode head) {
        if (head == null) {
            return true;
        }
        int left = depth(head.left);
        int right = depth(head.right);
        int diff = left - right;
        if (diff > 1 || diff < -1) {
            return false;
        }
        return isBalanced(head.left) && isBalanced(head.right);
    }
}

class BNode {
    int value;
    BNode left;
    BNode right;
}

以上每个节点被遍历多次。