How to Solve K Radius Subarray Averages Problem

You are given a 0-indexed array nums of n integers, and an integer k. The k-radius average for a subarray of nums centered at some index i with the radius k is the average of all elements in nums between the indices i - k and i + k (inclusive). If there are less than k elements before or after the index i, then the k-radius average is -1. Build and return an array avgs of length n where avgs[i] is the k-radius average for the subarray centered at index i. The average of x elements is the sum of the x elements divided by x, using integer division. The integer division truncates toward zero, which means losing its fractional part.