K Smallest Pairs (with Test Cases)

Given two integer arrays nums1 and nums2 sorted in non-decreasing order, and an integer k, return the k pairs (u, v) (where u is from nums1 and v is from nums2) with the smallest sums u+v. Requirements: Implement runnable code and write/add test cases to validate the output. The returned pairs should be ordered by increasing sum. If sums are tied, any order is acceptable. Input/Output Input: nums1, nums2, k Output: a list of the k smallest-sum pairs Constraints 0 <= len(nums1), len(nums2) <= 1e5 -1e9 <= nums1[i], nums2[j] <= 1e9 0 <= k <= 1e4 nums1 and nums2 are already sorted (non-decreasing) Sample Tests nums1=[1,7,11], nums2=[2,4,6], k=3 → [[1,2],[1,4],[1,6]] nums1=[1,1,2], nums2=[1,2,3], k=2 → [[1,1],[1,1]] nums1=[1,2], nums2=[3], k=3 → [[1,3],[2,3]] nums1=[], nums2=[1,2], k=5 → [] nums1=[-5,-2,0], nums2=[-3,1,4], k=4 → [[-5,-3],[-2,-3],[-5,1],[0,-3]] (any order for ties) Example Input nums1=[1,7,11] nums2=[2,4,6] k=3 Output [[1,2],[1,4],[1,6]]