a. You are given an array of n integers. Design an algorithm find a pair to find all unique pairs of elements(x,y) whose summation is S. your alogirthm must run in O(n log n ) time

b. You are given multipel arays of strings, wehre different string may have different number of characters. Design an algorithm make a set running in O(n log n time) where the algoirthm returns an union set of strings by combingin all arays and removing any duplicates

c. Suppose we hav an array of n positive integers range from 0 to n-1. design an algorithm that sorts the array in O(n) time