<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 Node
{
public:
    int data;
    int row;
    int col;

    Node(int d, int r, int c)
    {
        data = d;
        row = r;
        col = c;
    }
};

class compare
{
public:
    bool operator()(Node *a, Node *b)
    {
        return a->data > b->data;
    }
};

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

        priority_queue<Node *, vector<Node *>, compare> pq;

        for(int i=0 ; i<nums.size() ; i++){
            maxi = max(maxi , nums[i][0]);
            mini = min(mini , nums[i][0]);
            Node* temp = new Node(nums[i][0] , i , 0);
            pq.push(temp);
        }

        int ansStart = mini;
        int ansEnd = maxi;

        while(!pq.empty()){
            Node* topNode = pq.top();
            int topElement = topNode->data;
            int topRow = topNode->row;
            int topCol = topNode->col;
            pq.pop();

            mini = topElement;
            int currRange = maxi - mini;
            int ansRange = ansEnd - ansStart;

            if(ansRange > currRange){
                ansStart = mini;
                ansEnd = maxi;
            }

            if(topCol + 1 < nums[topRow].size()){
                maxi = max(maxi , nums[topRow][topCol+1]);
                Node* temp = new Node(nums[topRow][topCol+1] , topRow , topCol+1);
                pq.push(temp);
            }
            else{
                break;
            }
        }

        vector<int>ans;
        ans.push_back(ansStart);
        ans.push_back(ansEnd);

        return ans;
    }
};
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