I Problem

Given an integer array nums, find the subarray with the largest sum, and return its sum.

Example 1
Input: nums = [-2, 1, -3, 4, -1, 2, 1, -5, 4]
Output: 6
Explanation: The subarray [4, -1, 2, 1] has the largest sum 6.

I Problem

Given the head of a singly linked list where elements are sorted in ascending order, convert it to a height-balanced binary search tree.

Example 1

Input: head = [-10, -3, 0, 5, 9]
Output: [0, -3, 9, -10, null, 5]
Explanation: One possible answer is [0, -3, 9, -10, null, 5], which represents the shown height balanced BST.

I Problem

Given an integer array nums where the elements are sorted in ascending order, convert it to a height-balanced binary search tree.

Example 1

Input: nums = [-10, -3, 0, 5, 9]
Output: [0, -3, 9, -10, null, 5]
Explanation: [0, -10, 5, null, -3, null, 9] is also accepted:

I Problem

You are given an integer array nums with no duplicates. A maximum binary tree can be built recursively from nums using the following algorithm:

1. Create a root node whose value is the maximum value in nums.
2. Recursively build the left subtree on the subarray prefix to the left of the maximum value.
3. Recursively build the right subtree on the subarray suffix to the right of the maximum value.

I Problem

Given two integer arrays inorder and postorder where inorder is the inorder traversal of a binary tree and postorder is the postorder traversal of the same tree, construct and return the binary tree.

Example 1

Input: inorder = [9, 3, 15, 20, 7], postorder = [9, 15, 7, 20, 3]
Output: [3, 9, 20, null, null, 15, 7]

I Problem

Given two integer arrays preorder and inorder where preorder is the preorder traversal of a binary tree and inorder is the inorder traversal of the same tree, construct and return the binary tree.

Example 1

Input: preorder = [3, 9, 20, 15, 7], inorder = [9, 3, 15, 20, 7]
Output: [3, 9, 20, null, null, 15, 7]

I Problem

Given an integer array nums and an integer k, return the k most frequent elements. You may return the answer in any order.

Example 1
Input: nums = [1, 1, 1, 2, 2, 3], k = 2
Output: [1, 2]