Print all the sum pairs which occur maximum number of times

Given an array arr[] of N distinct integers. The task is to find the sum of two array integers a[i] + a[j] which occurs maximum number of times. In the case of multiple answers, print all of them.

Examples:

Input: arr[] = {1, 8, 3, 11, 4, 9, 2, 7}
Output:
10
12
11
The sum 10, 12 and 11 occur 3 times
7 + 4 = 11, 8 + 3 = 11, 9 + 2 = 11
1 + 9 = 10, 8 + 2 = 10, 7 + 3 = 10
1 + 11 = 12, 8 + 4 = 12, 9 + 3 = 12



Input: arr[] = {3, 1, 7, 11, 9, 2, 12}
Output:
12
14
10
13

Approach: The following steps can be followed to solve the problem:

  • Iterate over every pair of elements.
  • Use a hash-table to count the number of times every sum pair occurs.
  • At the end iterate over the hash-table and find the sum pair which occurs the maximum number of times.

Below is the implementation of the above approach:

C++

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// C++ implementation of the approach
#include <bits/stdc++.h>
using namespace std;
  
// Function to find the sum pairs
// that occur the most
void findSumPairs(int a[], int n)
{
    // Hash-table
    unordered_map<int, int> mpp;
    for (int i = 0; i < n - 1; i++) {
        for (int j = i + 1; j < n; j++) {
  
            // Keep a count of sum pairs
            mpp[a[i] + a[j]]++;
        }
    }
  
    // Variables to store
    // maximum occurrence
    int occur = 0;
  
    // Iterate in the hash table
    for (auto it : mpp) {
        if (it.second > occur) {
            occur = it.second;
        }
    }
  
    // Print all sum pair which occur
    // maximum number of times
    for (auto it : mpp) {
        if (it.second == occur)
            cout << it.first << endl;
    }
}
  
// Driver code
int main()
{
    int a[] = { 1, 8, 3, 11, 4, 9, 2, 7 };
    int n = sizeof(a) / sizeof(a[0]);
    findSumPairs(a, n);
  
    return 0;
}

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Java

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// Java implementation of above approach
import java.util.*;
  
class GFG 
{
  
// Function to find the sum pairs
// that occur the most
static void findSumPairs(int a[], int n)
{
    // Hash-table
    Map<Integer,Integer> mpp = new HashMap<>();
    for (int i = 0; i < n - 1; i++) 
    {
        for (int j = i + 1; j < n; j++) 
        {
  
            // Keep a count of sum pairs
            mpp.put(a[i] + a[j],mpp.get(a[i] + a[j])==null?1:mpp.get(a[i] + a[j])+1);
        }
    }
  
    // Variables to store
    // maximum occurrence
    int occur = 0;
  
    // Iterate in the hash table
    for (Map.Entry<Integer,Integer> entry : mpp.entrySet())
    {
        if (entry.getValue() > occur)
        {
            occur = entry.getValue();
        }
    }
  
    // Print all sum pair which occur
    // maximum number of times
    for (Map.Entry<Integer,Integer> entry : mpp.entrySet())
    {
        if (entry.getValue() == occur)
            System.out.println(entry.getKey());
    }
}
  
// Driver code
public static void main(String args[]) 
{
    int a[] = { 1, 8, 3, 11, 4, 9, 2, 7 };
    int n = a.length;
    findSumPairs(a, n);
}
}
  
/* This code is contributed by PrinciRaj1992 */

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Python3

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# Python 3 implementation of the approach
  
# Function to find the sum pairs
# that occur the most
def findSumPairs(a, n):
      
    # Hash-table
    mpp = {i:0 for i in range(21)}
    for i in range(n - 1):
        for j in range(i + 1, n, 1):
              
            # Keep a count of sum pairs
            mpp[a[i] + a[j]] += 1
  
    # Variables to store
    # maximum occurrence
    occur = 0
  
    # Iterate in the hash table
    for key, value in mpp.items():
        if (value > occur):
            occur = value
  
    # Print all sum pair which occur
    # maximum number of times
    for key, value in mpp.items():
        if (value == occur):
            print(key)
  
# Driver code
if __name__ == '__main__':
    a = [1, 8, 3, 11, 4, 9, 2, 7]
    n = len(a)
    findSumPairs(a, n)
  
# This code is contributed by
# Surendra_Gangwar

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C#

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// C# implementation of above approach
using System;
using System.Collections.Generic; 
      
class GFG 
{
  
// Function to find the sum pairs
// that occur the most
static void findSumPairs(int []a, int n)
{
    // Hash-table
    Dictionary<int,int> mpp = new Dictionary<int,int>();
    for (int i = 0; i < n - 1; i++) 
    {
        for (int j = i + 1; j < n; j++) 
        {
  
            // Keep a count of sum pairs
            if(mpp.ContainsKey(a[i] + a[j]))
            {
                var val = mpp[a[i] + a[j]];
                mpp.Remove(a[i] + a[j]);
                mpp.Add(a[i] + a[j], val + 1); 
            }
            else
            {
                mpp.Add(a[i] + a[j], 1);
            }
        }
    }
  
    // Variables to store
    // maximum occurrence
    int occur = 0;
  
    // Iterate in the hash table
    foreach(KeyValuePair<int, int> entry in mpp)
    {
        if (entry.Value > occur)
        {
            occur = entry.Value;
        }
    }
  
    // Print all sum pair which occur
    // maximum number of times
    foreach(KeyValuePair<int, int> entry in mpp)
    {
        if (entry.Value == occur)
            Console.WriteLine(entry.Key);
    }
}
  
// Driver code
public static void Main(String []args) 
{
    int []a = { 1, 8, 3, 11, 4, 9, 2, 7 };
    int n = a.Length;
    findSumPairs(a, n);
}
}
  
// This code is contributed by 29AjayKumar

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Output:

10
12
11


My Personal Notes arrow_drop_up

Striver(underscore)79 at Codechef and codeforces D

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