Kth smallest element in a sorted matrix

/*
Logic:
We can declare a min heap and put first elements from all the columns along with cordinates.
min heap will sort the elements based on the first component of each element.
pop top element from min heap and put the next element from that column only.
this way we will get elements one by one and return the kth element.
*/

class Solution {
public:
    int kthSmallest(vector<vector<int>>& matrix, int k) {        priority_queue<pair<int,pair<int,int>>,vector<pair<int,pair<int,int>>>,greater<pair<int,pair<int,int>>>> q;
        int n=matrix.size();
        for(int j=0;j<n;j++){
            q.push({matrix[0][j],{0,j}});
        }
        int count=0;
        while(!q.empty()){
            int val=q.top().first;
            pair<int,int> temp=q.top().second;

            if(++count==k) return val;
            q.pop();
            if(temp.first+1<n){ q.push({matrix[temp.first+1][temp.second],{temp.first+1,temp.second}});}
        }
        return 0;
    }
};