Binary Tree Tilt

给一个二叉树, 返回tilt, tilt的定义是左子树的和与右子树的和的绝对差. 简单的遍历一下就可以.

class Solution {
    int res = 0;
    public int findTilt(TreeNode root) {
        find(root);
        return res;
    }
    
    private int find(TreeNode node) {
        if(node == null)
            return 0;
        int left = find(node.left);
        int right = find(node.right);
        res += Math.abs(left - right);
        return left + right + node.val;
    }
}