1382. Balance a Binary Search Tree
https://leetcode.com/problems/balance-a-binary-search-tree/
Given a binary search tree, return a balanced binary search tree with the same node values.
A binary search tree is balanced if and only if the depth of the two subtrees of every node never differ by more than 1.
If there is more than one answer, return any of them.
Example 1:
Input: root = [1,null,2,null,3,null,4,null,null] Output: [2,1,3,null,null,null,4] Explanation: This is not the only correct answer, [3,1,4,null,2,null,null] is also correct.
Constraints:
- The number of nodes in the tree is between
1and10^4. - The tree nodes will have distinct values between
1and10^5.
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Intuition
Binary search tree in order traversal is ascending
Once we collect all nodes, we can run merge algo to create nodes
low = 0, high = nodes.size() - 1
mid is root node
low to mid - 1 is left node
mid + 1 to high is right node
recurse
if low > high return null
can happen for low, mid - 1 call if low = mid in calling function
If low == high -- one node .. return that as true
Rest is merge algo
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Related problems
convert-sorted-array-to-binary
convert-sorted-list-to-binary
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Time - O(n)
Space - O(n)
---
Intuition
Binary search tree in order traversal is ascending
Once we collect all nodes, we can run merge algo to create nodes
low = 0, high = nodes.size() - 1
mid is root node
low to mid - 1 is left node
mid + 1 to high is right node
recurse
if low > high return null
can happen for low, mid - 1 call if low = mid in calling function
If low == high -- one node .. return that as true
Rest is merge algo
---
Related problems
convert-sorted-array-to-binary
convert-sorted-list-to-binary
---
Time - O(n)
Space - O(n)
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