Select the Smallest Cross-Array Pair Sums

### Problem From two nondecreasing integer arrays nums1 and nums2, return k pairs [nums1[i],nums2[j]] having the smallest sums. Distinct index pairs count separately even if their values coincide. The source does not define tie-breaking between equal sums. ```cpp class Solution { public: vector<vector<int>> kSmallestPairs(vector<int>& nums1, vector<int>& nums2, int k); }; ``` ### Examples ```text nums1 = [0,3], nums2 = [1,4], k = 3 -> [[0,1],[0,4],[3,1]] nums1 = [2,2], nums2 = [-1], k = 2 -> [[2,-1],[2,-1]] ``` ### Constraints - Both lengths are 1 through 100000; both arrays are sorted nondecreasingly. - Values lie in [-1000000000,1000000000]. - 1 <= k <= 10000 and k <= nums1.length*nums2.length. ### Clarifying Questions Count index-pair occurrences, retain ties without inventing a mandatory tie rule, and avoid constructing the full Cartesian product. ```hint Inspect the contract For one fixed first-array index, in what order do its sums occur? ``` ### What a Strong Answer Covers Count index-pair occurrences, retain ties without inventing a mandatory tie rule, and avoid constructing the full Cartesian product. ### Follow-up Questions How should equal-valued pairs from different index choices be counted?