Sorting_Elements_Of_Arrays_By_Fraquency.cpp

//{ Driver Code Starts
#include <bits/stdc++.h>
using namespace std;


// } Driver Code Ends
class Solution {
  public:
    // Complete this function
    // Function to sort the array according to frequency of elements.
    vector<int> sortByFreq(vector<int>& arr) {
        map<int, int> mpp;
        vector<int> ans;
        vector<pair<int, int>> k;
        
        for(auto it : arr) mpp[it]++;
        for(auto it : mpp) k.push_back({it.second, it.first}); 
        
        sort(k.begin(), k.end(), [](pair<int, int>& a, pair<int, int>& b) 
        {
            if (a.first == b.first)  return a.second < b.second; 
            return a.first > b.first; 
        });
        
        for(auto it : k) 
        {
            for(int i = 0; i < it.first; i++)
                ans.push_back(it.second);
        }
        return ans;
    }
};

//{ Driver Code Starts.

int main() {

    int t;
    cin >> t;
    cin.ignore();
    while (t--) {

        string input;
        int num;
        vector<int> arr;

        getline(cin, input);
        stringstream s2(input);
        while (s2 >> num) {
            arr.push_back(num);
        }
        Solution obj;
        vector<int> v;
        v = obj.sortByFreq(arr);
        for (int i : v)
            cout << i << " ";
        cout << endl;
    }

    return 0;
}

// } Driver Code Ends