Find K Pairs with Smallest Sums

You are given two integer arrays `nums1` and `nums2` sorted in **non-decreasing order** and an integer `k`. Define a pair `(u, v)` which consists of one element from the first array and one element from the second array. Return _the_ `k` _pairs_ `(u1, v1), (u2, v2), ..., (uk, vk)` _with the smallest sums_.   **Example 1:** **Input:** nums1 = [1,7,11], nums2 = [2,4,6], k = 3 **Output:** [[1,2],[1,4],[1,6]] **Explanation:** The first 3 pairs are returned from the sequence: [1,2],[1,4],[1,6],[7,2],[7,4],[11,2],[7,6],[11,4],[11,6] ``` **Example 2:** **Input:** nums1 = [1,1,2], nums2 = [1,2,3], k = 2 **Output:** [[1,1],[1,1]] **Explanation:** The first 2 pairs are returned from the sequence: [1,1],[1,1],[1,2],[2,1],[1,2],[2,2],[1,3],[1,3],[2,3] ```   **Constraints:** - `1 <= nums1.length, nums2.length <= 105` - `-109 <= nums1[i], nums2[i] <= 109` - `nums1` and `nums2` both are sorted in **non-decreasing order**. - `1 <= k <= 104` - `k <= nums1.length * nums2.length`