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/*--- Below are 3 problems i have used hasing technique, After seeing below problems you'll be 100% clear on the basic hasing needed for competative programming First Repeating Element  Given an array arr[] of size N. The task is to find the first repeating element in an array of integers, i.e., an element that occurs more than once and whose index of first occurrence is smallest. Input : The first line contains an integer T denoting the total number of test cases. In each test cases, First line is number of elements in array N and second its values. Output: In each separate line print the index of first repeating element, if there is not any repeating element then print “-1” (without quotes). Use 1 Based Indexing. Constraints: 1 <= T <= 500 1 <= N <= 106 0 <= Ai <= 106 Example: Input: 1 7 1 5 3 4 3 5 6 Output: 2 Explanation: Testcase 1: 5 is appearing twice and its first appearence is at index 2 which is less than 3 whose first occur...

/*  TV Subscriptions (Hard Version) time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output The only difference between easy and hard versions is constraints. The BerTV channel every day broadcasts one episode of one of the  k k  TV shows. You know the schedule for the next  n n  days: a sequence of integers  a 1 , a 2 , … , a n a 1 , a 2 , … , a n  ( 1 ≤ a i ≤ k 1 ≤ a i ≤ k ), where  a i a i  is the show, the episode of which will be shown in  i i -th day. The subscription to the show is bought for the entire show (i.e. for all its episodes), for each show the subscription is bought separately. How many minimum subscriptions do you need to buy in order to have the opportunity to watch episodes of purchased shows  d d  ( 1 ≤ d ≤ n 1 ≤ d ≤ n ) days in a row? In other words, you want to buy the minimum number of TV shows so that there is some segm...