2022-04-15 Daily-Challenge

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In: DailyChallenge

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

April LeetCoding Challenge 15

Description

Trim a Binary Search Tree

Given the root of a binary search tree and the lowest and highest boundaries as low and high, trim the tree so that all its elements lies in [low, high]. Trimming the tree should not change the relative structure of the elements that will remain in the tree (i.e., any node's descendant should remain a descendant). It can be proven that there is a unique answer.

Return the root of the trimmed binary search tree. Note that the root may change depending on the given bounds.

Example 1:

img

Input: root = [1,0,2], low = 1, high = 2
Output: [1,null,2]

Example 2:

img

Input: root = [3,0,4,null,2,null,null,1], low = 1, high = 3
Output: [3,2,null,1]

Constraints:

  • The number of nodes in the tree in the range [1, 10^4].
  • 0 <= Node.val <= 10^4
  • The value of each node in the tree is unique.
  • root is guaranteed to be a valid binary search tree.
  • 0 <= low <= high <= 10^4

Solution

auto speedup = [](){
  cin.tie(nullptr);
  cout.tie(nullptr);
  ios::sync_with_stdio(false);
  return 0;
}();
class Solution {
public:
  TreeNode* trimBST(TreeNode* root, int low, int high) {
    if(!root) return root;
    if(root->val < low) return trimBST(root->right, low, high);
    if(root->val > high) return trimBST(root->left, low, high);
    while(root->left && root->left->val < low) root->left = root->left->right;
    root->left = trimBST(root->left, low, high);
    while(root->right && root->right->val > high) root->right = root->right->left;
    root->right = trimBST(root->right, low, high);
    return root;
  }
};

// Accepted
// 78/78 cases passed (7 ms)
// Your runtime beats 99.34 % of cpp submissions
// Your memory usage beats 7.34 % of cpp submissions (24.1 MB)
Algorithm