https://leetcode.com/problems/kth-smallest-element-in-a-bst/?envType=study-plan-v2&envId=top-interview-150 class Solution { public: int c = 0; int ans = 0; int kthSmallest(TreeNode* root, int k)

https://leetcode.com/problems/minimum-absolute-difference-in-bst/description/?envType=study-plan-v2&envId=top-interview-150 class Solution { public: int ans; pair<int, int> dfs(TreeNode *cur) { if

https://leetcode.com/problems/binary-tree-zigzag-level-order-traversal/description/?envType=study-plan-v2&envId=top-interview-150 class Solution { public: vector<vector<int>> zigzagLevelOrder(TreeNode* root) { if

https://leetcode.com/problems/binary-tree-right-side-view/description/?envType=study-plan-v2&envId=top-interview-150 class Solution { public: vector<int> rightSideView(TreeNode* root) { if (root == NULL) return