<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) {
       
       priority_queue<pair<int,vector<int>>, vector<pair<int,vector<int>>>, greater<pair<int,vector<int>>>> pq;

       vector<vector<int>> res;
        set<pair<int,int>> visited;
       vector<int> temp = {0, 0};

       visited.insert({0,0});

       pq.push(make_pair(nums1[0]+nums2[0], temp));
       // int i =0, j =0;
        int m = nums1.size(); 
        int n = nums2.size();
       while(k-- && !pq.empty()){
            vector<int>vec = pq.top().second;
             pq.pop();
            int i = vec[0];
            int j =vec[1];
           // cout << i << " " << j <<"\n";
            vector<int> temp1 = {nums1[i],nums2[j]};
            res.push_back(temp1);
           
            if( i+1 < m && visited.find({i+1,j}) == visited.end()){
              //  cout << "yo\n";
           vector<int> temp3 = {i+1,j};
            pq.push(make_pair(nums1[i+1]+nums2[j], temp3));
            visited.insert({i+1,j});
            }

            if( j+1 < n && visited.find({i,j+1}) == visited.end()){
             //   cout << "go\n";
                temp.clear();
                vector<int> temp4 = {i,j+1};
                
                pq.push(make_pair(nums1[i]+nums2[j+1], temp4));
                visited.insert({i,j+1});
            }
       }

       return res;
    
    }
};
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