2098. Subsequence of Size K With the Largest Even Sum
You are given an integer array nums and an integer k. Find the largest even sum of any subsequence of nums that has a length of k.
Return this sum, or -1 if such a sum does not exist.
A subsequence is an array that can be derived from another array by deleting some or no elements without changing the order of the remaining elements.
1780. Check if Number is a Sum of Powers of Three
Given an integer n, return true if it is possible to represent n as the sum of distinct powers of three. Otherwise, return false.
An integer y is a power of three if there exists an integer x such that y == 3x.
1664. Ways to Make a Fair Array
You are given an integer array nums. You can choose exactly one index (0-indexed) and remove the element. Notice that the index of the elements may change after the removal.
For example, if nums = [6,1,7,4,1]:
- Choosing to remove index 1 results in nums = [6,7,4,1].
- Choosing to remove index 2 results in nums = [6,1,4,1].
- Choosing to remove index 4 results in nums = [6,1,7,4].
An array is fair if the sum of the odd-indexed values equals the sum of the even-indexed values.
Return the number of indices that you could choose such that after the removal, nums is fair.
The diameter of a tree is the number of edges in the longest path in that tree.
There is an undirected tree of n nodes labeled from 0 to n - 1. You are given a 2D array edges where edges.length == n - 1 and edges[i] = [ai, bi] indicates that there is an undirected edge between nodes ai and bi in the tree.
Return the diameter of the tree.
Given an m x n picture consisting of black ‘B’ and white ‘W’ pixels, return the number of black lonely pixels.
A black lonely pixel is a character ‘B’ that located at a specific position where the same row and same column don’t have any other black pixels.