You are given two integer arrays, nums1 and nums2, both sorted in non-decreasing order. You are also given two integers, m and n, representing the number of elements in nums1 and nums2, respectively.

Your task is to merge the elements of nums2 into nums1 so that nums1 becomes a single array sorted in non-decreasing order.

The merged result is stored in nums1, which has a total length of m + n. The first m positions contain the initial elements, the last n positions are placeholders (initialized to 0), and nums2 contains the n elements to merge.