[LeetCode] Find the Distance Value Between Two Arrays

1385. Find the Distance Value Between Two Arrays

Given two integer arrays arr1 and arr2, and the integer d, return the distance value between the two arrays.

The distance value is defined as the number of elements arr1[i] such that there is not any element arr2[j] where |arr1[i]-arr2[j]| <= d.

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[LeetCode] Valid Perfect Square

367. Valid Perfect Square

Given a positive integer num, write a function which returns True if num is a perfect square else False.

Follow up: Do not use any built-in library function such as sqrt.

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[LeetCode] Sum of Subarray Ranges

2104. Sum of Subarray Ranges

You are given an integer array nums. The range of a subarray of nums is the difference between the largest and smallest element in the subarray.

Return the sum of all subarray ranges of nums.

A subarray is a contiguous non-empty sequence of elements within an array.

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[LeetCode] Maximum Binary Tree

654. Maximum Binary Tree

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

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

Return the maximum binary tree built from nums.

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[LeetCode] Next Greater Node In Linked List

1019. Next Greater Node In Linked List

You are given the head of a linked list with n nodes.

For each node in the list, find the value of the next greater node. That is, for each node, find the value of the first node that is next to it and has a strictly larger value than it.

Return an integer array answer where answer[i] is the value of the next greater node of the ith node (1-indexed). If the ith node does not have a next greater node, set answer[i] = 0.

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[LeetCode] Maximum Width Ramp

962. Maximum Width Ramp

A ramp in an integer array nums is a pair (i, j) for which i < j and nums[i] <= nums[j]. The width of such a ramp is j - i.

Given an integer array nums, return the maximum width of a ramp in nums. If there is no ramp in nums, return 0.

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[LeetCode] Number Of Ways To Reconstruct A Tree

1719. Number Of Ways To Reconstruct A Tree

You are given an array pairs, where pairs[i] = [xi, yi], and:

  • There are no duplicates.
  • xi < yi

Let ways be the number of rooted trees that satisfy the following conditions:

  • The tree consists of nodes whose values appeared in pairs.
  • A pair [xi, yi] exists in pairs if and only if xi is an ancestor of yi or yi is an ancestor of xi.
  • Note: the tree does not have to be a binary tree.

Two ways are considered to be different if there is at least one node that has different parents in both ways.

Return:

  • 0 if ways == 0
  • 1 if ways == 1
  • 2 if ways > 1

A rooted tree is a tree that has a single root node, and all edges are oriented to be outgoing from the root.

An ancestor of a node is any node on the path from the root to that node (excluding the node itself). The root has no ancestors.

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[LeetCode] Even Odd Tree

1609. Even Odd Tree

A binary tree is named Even-Odd if it meets the following conditions:

  • The root of the binary tree is at level index 0, its children are at level index 1, their children are at level index 2, etc.
  • For every even-indexed level, all nodes at the level have odd integer values in strictly increasing order (from left to right).
  • For every odd-indexed level, all nodes at the level have even integer values in strictly decreasing order (from left to right).

Given the root of a binary tree, return true if the binary tree is Even-Odd, otherwise return false.

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[LeetCode] Validate Binary Tree Nodes

1361. Validate Binary Tree Nodes

You have n binary tree nodes numbered from 0 to n - 1 where node i has two children leftChild[i] and rightChild[i], return true if and only if all the given nodes form exactly one valid binary tree.

If node i has no left child then leftChild[i] will equal -1, similarly for the right child.

Note that the nodes have no values and that we only use the node numbers in this problem.

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[LeetCode] Sum of Nodes with Even-Valued Grandparent

1315. Sum of Nodes with Even-Valued Grandparent

Given the root of a binary tree, return the sum of values of nodes with an even-valued grandparent. If there are no nodes with an even-valued grandparent, return 0.

A grandparent of a node is the parent of its parent if it exists.

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