Sliding Window Mex

You are given an array of n integers. Your task is to calculate the mex of each window of k elements, from left to right. The mex is the smallest nonnegative integer that does not appear in the array. For example, the mex for [3,1,4,3,0,5] is 2. Input The first line contains two integers n and k: the number of elements and the size of the window. Then there are n integers x_1,x_2,\ldots,x_n: t