501. Find Mode in Binary Search Tree

https://leetcode.com/problems/find-mode-in-binary-search-tree/description/
Solution 1: In-order traversal
mx: max count of different values
cnt: counting the duplicates
preVal: previous checked value
    void inOrder(TreeNode* node, vector<int>& mode, int& mx, int& cnt, int& preVal) {
        if(!node) return;
        inOrder(node->left, mode, mx, cnt, preVal);
        if(cnt == 0) {
            cnt = 1;
            preVal = node->val;
        }
        else if(node->val == preVal) cnt++;
        else {
            if(mx == cnt) mode.push_back(preVal);
            else if(mx < cnt) {
                mx = cnt;
                mode.clear();
                mode.push_back(preVal);
            }
            preVal = node->val;
            cnt = 1;
        }
        inOrder(node->right, mode, mx, cnt, preVal);
    }
    vector<int> findMode(TreeNode* root) {
        vector<int> mode;
        if(!root) return mode;
        int mx = 0, cnt = 0, preVal;
        inOrder(root, mode, mx, cnt, preVal);
        if(mx < cnt) return {preVal};
        if(mx == cnt) mode.push_back(preVal);
        return mode;
    }
Solution 2. We can always do an in-order tree traversal and store the numbers in an array and then search for the mode.