<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:
    bool allrangesUsed(std::vector<int> &ranges){
        for(auto n:ranges) if (n == 0) return false;
        return true;
    }
    vector<int> smallestRange(vector<vector<int>>& nums) {
        auto cmp = [](const std::pair<int,int> &p1, const std::pair<int,int> &p2){
            return p1.first > p2.first;
        };

        std::priority_queue<std::pair<int,int>, std::vector<std::pair<int,int>>,decltype(cmp)> pq(cmp);

        for(int i=0;i<nums.size();++i){
            for(int j=0;j<nums[i].size();++j){
                pq.emplace(nums[i][j],i);
            }
        }

        std::vector<std::pair<int,int>> sorted_nums;
        while(!pq.empty()){
            sorted_nums.push_back(pq.top());
            pq.pop();
        }

        std::vector<int> ranges_used(nums.size(),0);

        int l{0};
        int min_range_l {INT_MAX};
        std::pair<int,int> min_range {-1,-1};
        for(int r=0; r<sorted_nums.size(); ++r){
            ++ranges_used[sorted_nums[r].second];
            while(allrangesUsed(ranges_used)){
                if (sorted_nums[r].first - sorted_nums[l].first < min_range_l){
                    min_range_l = sorted_nums[r].first - sorted_nums[l].first;
                    min_range = {sorted_nums[l].first, sorted_nums[r].first};
                }
                --ranges_used[sorted_nums[l++].second];
            }
        }

        return {min_range.first, min_range.second};
    }
};
23973