You are given a binary matrix with 2 rows and n columns, where each element is either 0 or 1. The sum of elements in the 0-th (upper) row is given by upper, the sum of elements in the 1-st (lower) row is given by lower, and the column-wise sum is given by colsum. Your task is to reconstruct the matrix based on these sums. If reconstruction is not possible, return an empty matrix.
Given an array where each element represents the required size of the group for each person, group the people accordingly and return the groups. Each person must be in exactly one group.
Given a string palindrome that is a palindrome, you need to replace exactly one character with any lowercase English letter such that the resulting string is no longer a palindrome. The resulting string should be the lexicographically smallest string possible. If it is not possible to change the string to make it non-palindromic, return an empty string.
You are given an integer array arr. You can choose a set of integers and remove all occurrences of these integers. Your task is to return the minimum size of the set such that at least half of the integers of the array are removed.