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669.trim-a-binary-search-tree.cpp
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63 lines (59 loc) · 1.92 KB
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// Tag: Tree, Depth-First Search, Binary Search Tree, Binary Tree
// Time: O(N)
// Space: O(H)
// Ref: -
// Note: -
// 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:
//
//
// Input: root = [1,0,2], low = 1, high = 2
// Output: [1,null,2]
//
// Example 2:
//
//
// 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 is in the range [1, 104].
// 0 <= Node.val <= 104
// The value of each node in the tree is unique.
// root is guaranteed to be a valid binary search tree.
// 0 <= low <= high <= 104
//
//
/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode() : val(0), left(nullptr), right(nullptr) {}
* TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
* TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
* };
*/
class Solution {
public:
TreeNode* trimBST(TreeNode* root, int low, int high) {
if (!root) {
return nullptr;
}
if (root->val >= low && root->val <= high) {
root->left = trimBST(root->left, low, high);
root->right = trimBST(root->right, low, high);
return root;
}
if (root->val > high) {
return trimBST(root->left, low, high);
} else {
return trimBST(root->right, low, high);
}
}
};