<p>You have <code>k</code> lists of sorted integers in <strong>non-decreasing&nbsp;order</strong>. Find the <b>smallest</b> range that includes at least one number from each of the <code>k</code> lists.</p>

<p>We define the range <code>[a, b]</code> is smaller than range <code>[c, d]</code> if <code>b - a &lt; d - c</code> <strong>or</strong> <code>a &lt; c</code> if <code>b - a == d - c</code>.</p>

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

<pre>
<strong>Input:</strong> nums = [[4,10,15,24,26],[0,9,12,20],[5,18,22,30]]
<strong>Output:</strong> [20,24]
<strong>Explanation: </strong>
List 1: [4, 10, 15, 24,26], 24 is in range [20,24].
List 2: [0, 9, 12, 20], 20 is in range [20,24].
List 3: [5, 18, 22, 30], 22 is in range [20,24].
</pre>

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

<pre>
<strong>Input:</strong> nums = [[1,2,3],[1,2,3],[1,2,3]]
<strong>Output:</strong> [1,1]
</pre>

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

<ul>
	<li><code>nums.length == k</code></li>
	<li><code>1 &lt;= k &lt;= 3500</code></li>
	<li><code>1 &lt;= nums[i].length &lt;= 50</code></li>
	<li><code>-10<sup>5</sup> &lt;= nums[i][j] &lt;= 10<sup>5</sup></code></li>
	<li><code>nums[i]</code>&nbsp;is sorted in <strong>non-decreasing</strong> order.</li>
</ul>

class Info{
    public:
    int val;
    int row;
    int col;

    Info(int a, int b, int c){
        this->val = a;
        this->row = b;
        this->col = c;
    }
};

class Comp{
    public:
    bool operator()(Info* a, Info* b){
        return a->val > b->val;
    }
};

class Solution {
public:
    vector<int> smallestRange(vector<vector<int>>& nums) {
        int mini = INT_MAX;
        int maxi = INT_MIN;

        priority_queue< Info*, vector<Info*>, Comp> pq;
        //putting initial elements
        for(int i = 0; i < nums.size(); i++){
            int element = nums[i][0];

            Info* temp = new Info(element, i, 0);
            pq.push(temp);

            maxi = max(maxi, element);
            mini = min(mini, element);
        }   

        int ansStart = mini;
        int ansEnd = maxi;
        // cout<<mini<<" "<<maxi<<" ";


        while(!pq.empty()){
            Info* temp = pq.top();
            pq.pop();

            int colIndex = temp->col;
            int rowIndex = temp->row;
            mini = temp->val; 

            if(ansEnd - ansStart > maxi - mini){
                ansStart = mini;
                ansEnd = maxi;
            } 
            
            if(colIndex + 1 < nums[rowIndex].size()){
                Info *newNode = new Info(nums[rowIndex][colIndex+1], rowIndex, colIndex +1 );
                pq.push(newNode);  
                maxi = max(maxi, nums[rowIndex][colIndex + 1]);
                
            }else{
                break;
            }

            


            delete temp;
        }

        return {ansStart, ansEnd};
    }
};
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