Today I have done leetcode's February LeetCoding Challenge with cpp.

February LeetCoding Challenge 17

Description

Minimum Distance Between BST Nodes

Given the root of a Binary Search Tree (BST), return the minimum difference between the values of any two different nodes in the tree.

Example 1:

Input: root = [4,2,6,1,3]
Output: 1

Example 2:

Input: root = [1,0,48,null,null,12,49]
Output: 1

Constraints:

• The number of nodes in the tree is in the range [2, 100].
• 0 <= Node.val <= 105

Note: This question is the same as 530: https://leetcode.com/problems/minimum-absolute-difference-in-bst/

Solution

class Solution {
  int answer = INT_MAX;
  void solve(TreeNode* root, set<int> &st) {
    if(!root) return;
    // cout << root->val << ' ' << answer << ' ';
    if(st.size()) {
      auto lessIt = st.upper_bound(root->val);
      if(lessIt != st.begin()) {
        --lessIt;
        // cout << "less " << *lessIt << ' ';
        answer = min(answer, root->val - *lessIt);
      }
      auto moreOrEqualIt = st.lower_bound(root->val);
      if(moreOrEqualIt != st.end()) {
        // cout << "more " << *moreOrEqualIt;
        answer = min(answer, *moreOrEqualIt - root->val);
      }
    }
    // cout << endl;
    st.insert(root->val);
    solve(root->left, st);
    solve(root->right, st);
  }
public:
  int minDiffInBST(TreeNode* root) {
    set<int> st;
    solve(root, st);
    return answer;
  }
};

// Accepted
// 48/48 cases passed (3 ms)
// Your runtime beats 67.12 % of cpp submissions
// Your memory usage beats 6.62 % of cpp submissions (11.6 MB)