B'The easy and hard versions of this problem differ only in the constraints on n . In the hard version, the sum of values of n over all test cases does not exceed 2 cdot 10^5 . Furthermore, there are no additional constraints on the value of n in a single test case. There are 2n light bulbs arranged in a row. Each light bulb has a color from 1 to n (exactly two light bulbs for each color). Initially, all light bulbs are turned off. You choose a set of light bulbs S that you initially turn on. After that, you can perform the following operations in any order any number of times: You want to choose a set of light bulbs S that you initially turn on in such a way that by performing the described operations, you can ensure that all light bulbs are turned on. Calculate two numbers: The first line of the input contains a single integer t ( 1 <= t <= 10^4 ) -- the number of test cases. Then follow the descriptions of the test cases. The first line of each test case contains a single integer n ( 2 <= n <= 2 cdot 10^5 ) -- the number of pairs of light bulbs. The second line of each test case contains 2n integers c_1, c_2, ... , c_{2n} ( 1 <= c_i <= n ), where c_i is the color of the i -th light bulb. For each color from 1 to n , exactly two light bulbs have this color. Additional constraint on the input: the sum of values of n over all test cases does not exceed 2 cdot 10^5 . For each test case, output two integers: '...