<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 Solution {
public:
    class Info {
    public:
        int data;
        int rowInd;
        int colInd;

        Info(int data, int rowInd, int colInd) {
            this->data = data;
            this->rowInd = rowInd;
            this->colInd = colInd;
        }
    };

    class compare {
    public:
        bool operator()(Info* a, Info* b) { return a->data > b->data; }
    };
    vector<int> smallestRange(vector<vector<int>>& nums) {
        priority_queue<Info*, vector<Info*>, compare> pq;
        int maxi = INT_MIN;
        int a, b;
        for (int i = 0; i < nums.size(); i++) {
            int ele = nums[i][0];
            Info* temp = new Info(ele, i, 0);
            pq.push(temp);
            maxi = max(maxi, ele);
        }

        a = pq.top()->data;
        b = maxi;

        while (!pq.empty()) {
            Info* topNode = pq.top();
            int topRow = topNode->rowInd;
            int topCol = topNode->colInd;
            pq.pop();

            if (topCol + 1 < nums[topRow].size()) {
                int ele = nums[topRow][topCol + 1];
                maxi = max(maxi, ele);

                Info* newNode = new Info(ele, topRow, topCol + 1);
                pq.push(newNode);
                int currA = pq.top()->data;
                int currB = maxi;
                if ((currB - currA) < (b - a)) {
                    b = currB;
                    a = currA;
                }
            } else {
                break;
            }
        }
        vector<int> ans;
        ans.push_back(a);
        ans.push_back(b);
        return ans;
    }
};
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