Elements of first array that have more frequencies

Given two arrays (which may or may not be sorted). There arrays are such that they might have some common elements in them. We need to find elements whose counts of occurrences are more in first array than second.

Examples:

Input : ar1[] = {1, 2, 2, 2, 3, 3, 4, 5}
        ar2[] = {2, 2, 3, 3, 3, 4}
Output : 1 2 5
1 occurs one times in first and zero times in second
2 occurs three times in first and two times in second
............................

Input : ar1[] = {1, 3, 4, 2, 3}
        ar2[] = {3, 4, 5}
Output : 3

Recommended: Please try your approach on {IDE} first, before moving on to the solution.

The idea is to use hashing. We traverse first array and insert all elements and their frequencies in a hash table. Now we traverse through the second array and reduce frequencies in hash table for the common elements. Now we traverse through first array again and print those elements whose frequencies are still more than 0. To avoid repeated printing of same elements, we set frequency as 0.

C++

// C++ program to print all those elements of 
// first array that have more frequencies than 
// second array. 
#include <bits/stdc++.h> 
using namespace std; 
  
// Compares two intervals according to staring times. 
void moreFreq(int ar1[], int ar2[], int m, int n) 
{ 
    // Traverse first array and store frequencies 
    // of all elements 
    unordered_map<int, int> mp; 
    for (int i = 0; i < m; i++) 
        mp[ar1[i]]++; 
  
    // Traverse second array and reduce frequencies 
    // of common elements. 
    for (int i = 0; i < n; i++) 
        if (mp.find(ar2[i]) != mp.end()) 
            mp[ar2[i]]--; 
  
    // Now traverse first array again and print 
    // all those elements whose frequencies are 
    // more than 0. To avoid repeated printing, 
    // we set frequency as 0 after printing. 
    for (int i = 0; i < m; i++) { 
        if (mp[ar1[i]] > 0) { 
            cout << ar1[i] << " "; 
            mp[ar1[i]] = 0; 
        } 
    } 
} 
  
// Driver code 
int main() 
{ 
    int ar1[] = { 1, 2, 2, 2, 3, 3, 4, 5 }; 
    int ar2[] = { 2, 2, 3, 3, 3, 4 }; 
    int m = sizeof(ar1) / sizeof(ar1[0]); 
    int n = sizeof(ar2) / sizeof(ar2[0]); 
    moreFreq(ar1, ar2, m, n); 
    return 0; 
} 

Java

// Java program to print all those elements of 
// first array that have more frequencies than 
// second array. 
import java.util.*; 
  
class GFG 
{ 
  
    // Compares two intervals according to staring times. 
    static void moreFreq(int ar1[], int ar2[], int m, int n) 
    { 
        // Traverse first array and store frequencies 
        // of all elements 
        Map<Integer,Integer> mp = new HashMap<>(); 
        for (int i = 0 ; i < m; i++) 
        { 
            if(mp.containsKey(ar1[i])) 
            { 
                mp.put(ar1[i], mp.get(ar1[i])+1); 
            } 
            else
            { 
                mp.put(ar1[i], 1); 
            } 
        } 
          
        // Traverse second array and reduce frequencies 
        // of common elements. 
        for (int i = 0; i < n; i++) 
            if (mp.containsKey(ar2[i])) 
                mp.put(ar2[i], mp.get(ar2[i])-1); 
      
        // Now traverse first array again and print 
        // all those elements whose frequencies are 
        // more than 0. To avoid repeated printing, 
        // we set frequency as 0 after printing. 
        for (int i = 0; i < m; i++)  
        { 
            if (mp.get(ar1[i]) > 0)  
            { 
                System.out.print(ar1[i] + " "); 
                mp.put(ar1[i], 0); 
            } 
        } 
    } 
      
    // Driver code 
    public static void main(String[] args)  
    { 
        int ar1[] = { 1, 2, 2, 2, 3, 3, 4, 5 }; 
        int ar2[] = { 2, 2, 3, 3, 3, 4 }; 
        int m = ar1.length; 
        int n = ar2.length; 
        moreFreq(ar1, ar2, m, n); 
    } 
} 
  
// This code has been contributed by 29AjayKumar 

Python3

# Python3 program to print all those elements of 
# first array that have more frequencies than 
# second array. 
import math as mt 
  
# Compares two intervals according to 
# staring times. 
def moreFreq(ar1, ar2, m, n): 
  
    # Traverse first array and store  
    # frequencies of all elements 
    mp = dict() 
    for i in range(m): 
        if ar1[i] in mp.keys(): 
            mp[ar1[i]] += 1
        else: 
            mp[ar1[i]] = 1
                  
    # Traverse second array and reduce  
    # frequencies of common elements. 
    for i in range(n): 
        if ar2[i] in mp.keys(): 
            mp[ar2[i]] -= 1
  
    # Now traverse first array again and print 
    # all those elements whose frequencies are 
    # more than 0. To avoid repeated printing, 
    # we set frequency as 0 after printing. 
    for i in range(m): 
        if (mp[ar1[i]] > 0): 
            print(ar1[i], end = " ") 
            mp[ar1[i]] = 0
                                  
# Driver code 
ar1 = [ 1, 2, 2, 2, 3, 3, 4, 5 ] 
ar2 = [ 2, 2, 3, 3, 3, 4 ] 
m = len(ar1) 
n = len(ar2)  
moreFreq(ar1, ar2, m, n) 
  
# This code is contributed  
# by mohit kumar 29 

C#

// C# pprogram to print all those elements of  
// first array that have more frequencies than  
// second array.  
using System; 
using System.Collections.Generic; 
  
class GFG  
{  
  
    // Compares two intervals according to 
    // staring times.  
    static void moreFreq(int []ar1, int []ar2, 
                         int m, int n)  
    {  
        // Traverse first array and store frequencies  
        // of all elements  
        Dictionary<int,  
                   int> mp = new Dictionary<int,  
                                            int>();  
        for (int i = 0 ; i < m; i++)  
        {  
            if(mp.ContainsKey(ar1[i]))  
            {  
                mp[ar1[i]] = mp[ar1[i]] + 1;  
            }  
            else
            {  
                mp.Add(ar1[i], 1);  
            }  
        }  
          
        // Traverse second array and reduce frequencies  
        // of common elements.  
        for (int i = 0; i < n; i++)  
            if (mp.ContainsKey(ar2[i]))  
                mp[ar2[i]] = mp[ar2[i]] - 1;  
      
        // Now traverse first array again and print  
        // all those elements whose frequencies are  
        // more than 0. To avoid repeated printing,  
        // we set frequency as 0 after printing.  
        for (int i = 0; i < m; i++)  
        {  
            if (mp[ar1[i]] > 0)  
            {  
                Console.Write(ar1[i] + " ");  
                mp[ar1[i]] = 0;  
            }  
        }  
    }  
      
    // Driver code  
    public static void Main(String[] args)  
    {  
        int []ar1 = { 1, 2, 2, 2, 3, 3, 4, 5 };  
        int []ar2 = { 2, 2, 3, 3, 3, 4 };  
        int m = ar1.Length;  
        int n = ar2.Length;  
        moreFreq(ar1, ar2, m, n);  
    }  
}  
  
// This code is contributed by 29AjayKumar  

Output:

1 2 5

Time Complexity : O(m + n) under the assumption that unordered_map find() and insert() work in O(1) time.

Attention reader! Don’t stop learning now. Get hold of all the important DSA concepts with the DSA Self Paced Course at a student-friendly price and become industry ready.

My Personal Notes

Recommended: Please try your approach on {IDE} first, before moving on to the solution.

C++

Java

Python3

C#

Recommended Posts: