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

June LeetCoding Challenge 14

Description

Minimum Absolute Difference in BST

Given the root of a Binary Search Tree (BST), return the minimum absolute 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, 104].
• 0 <= Node.val <= 105

Note: This question is the same as 783: https://leetcode.com/problems/minimum-distance-between-bst-nodes/

Solution

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

// Accepted
// 188/188 cases passed (27 ms)
// Your runtime beats 30.22 % of cpp submissions
// Your memory usage beats 5.25 % of cpp submissions (29.5 MB)