<p>You are given two integer arrays <code>nums1</code> and <code>nums2</code> sorted in <strong>non-decreasing&nbsp;order</strong> and an integer <code>k</code>.</p>

<p>Define a pair <code>(u, v)</code> which consists of one element from the first array and one element from the second array.</p>

<p>Return <em>the</em> <code>k</code> <em>pairs</em> <code>(u<sub>1</sub>, v<sub>1</sub>), (u<sub>2</sub>, v<sub>2</sub>), ..., (u<sub>k</sub>, v<sub>k</sub>)</code> <em>with the smallest sums</em>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> nums1 = [1,7,11], nums2 = [2,4,6], k = 3
<strong>Output:</strong> [[1,2],[1,4],[1,6]]
<strong>Explanation:</strong> 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]
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> nums1 = [1,1,2], nums2 = [1,2,3], k = 2
<strong>Output:</strong> [[1,1],[1,1]]
<strong>Explanation:</strong> 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]
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= nums1.length, nums2.length &lt;= 10<sup>5</sup></code></li>
	<li><code>-10<sup>9</sup> &lt;= nums1[i], nums2[i] &lt;= 10<sup>9</sup></code></li>
	<li><code>nums1</code> and <code>nums2</code> both are sorted in <strong>non-decreasing order</strong>.</li>
	<li><code>1 &lt;= k &lt;= 10<sup>4</sup></code></li>
	<li><code>k &lt;=&nbsp;nums1.length *&nbsp;nums2.length</code></li>
</ul>

class Solution {
public:
    vector<vector<int>> kSmallestPairs(vector<int>& nums1, vector<int>& nums2, int k) {
        vector<vector<int>> output;
        output.reserve(k);
        
        size_t nums1Size = nums1.size();
        size_t nums2Size = nums2.size();

        const int N = nums1Size < k ? nums1Size : k;
        std::vector<int> indices(N, 0);

        size_t index1 = 0;
        size_t index2 = 0;

        int count = 0;
        std::vector<int> aux(2);
        int minSum;
        int prevIndex;
        int sum;
        while (count < k ) {
            minSum = INT_MAX;
            prevIndex = -1;
            for(size_t i=0;i<nums1Size; ++i) {
                if ( prevIndex == 0 ) {
                    break;
                }
                if ( indices[i] < nums2Size ) {
                    sum = nums1[i] + nums2[indices[i]];
                    if ( sum < minSum) {
                        minSum = sum;
                        index1 = i;
                    }
                }
                prevIndex = indices[i];
            }
            
            index2 = indices[index1];
            //std::cout << index1 << " - " << index2 << "\n";
            indices[index1]++;

            aux[0] = nums1[index1];
            aux[1] = nums2[index2];
            output.push_back(aux);

            count++;
        }
        return output;
    }
};
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