LeetCode "Closest Binary Search Tree Value II"

I made it too complicated first.. It is really simply if full-tree in-order traversal is allowed.

class Solution 
{
    int inx, sofar; // closest
    bool bleft; // target on left of closest
    vector<int> nums;

    void go(TreeNode *p, double target)
    {
        if (!p) return;
        go(p->left, target);
        nums.push_back(p->val);
        if (abs(sofar - target) > abs(p->val - target))
        {
            inx = nums.size() - 1;
            sofar = p->val;
            bleft = target < p->val;
        }
        go(p->right, target);
    }
public:
    vector<int> closestKValues(TreeNode* root, double target, int k) 
    {
        sofar = std::numeric_limits<int>::min();
        go(root, target);

        size_t len = nums.size();
        int l = bleft ? inx - 1: inx;
        int r = bleft ? inx : inx + 1;

        vector<int> ret;
        while (k--)
        {
            if (l < 0)
            {
                ret.push_back(nums[r ++]);
            }
            else if (r == len)
            {
                ret.push_back(nums[l --]);
            }
            else
            {
                double succ_diff = abs(nums[r] - target);
                double pred_diff = abs(nums[l] - target);
                if (succ_diff < pred_diff)
                    ret.push_back(nums[r++]);
                else
                    ret.push_back(nums[l--]);
            }
        }
        return ret;
    }
};