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Length of smallest subarray consisting of all occurrences of all maximum occurring elements

  • Last Updated : 29 Jan, 2022

Given an array arr[] of size N, The task is to find the length of the smallest subarray consisting of all the occurrences of maximum occurring elements
Examples:

Input: arr[] = {1, 2, 1, 3, 2}
Output: 5
Explanation: Elements with maximum frequency (=2) are 1 & 2. 
Therefore, the length of smallest subarray consisting of all the occurrences of 1 and 2 is 5 i.e {1, 2, 1, 3, 2}

Input: arr[] = {1, 2, 5, 1, 5, 5}
Output: 4

 

Approach: The task can be solved by keeping track of the first & the last occurrences of the maximum occurring elements. The length of the smallest subarray would be the difference between the maximum of the last occurrences and the minimum of the first occurrences. 
Follow the below steps to solve the problem:

  • Create a map, to store the frequencies of the elements
  • Find the elements with maximum frequency, and store their first and last occurrences.
  • Finally, return the difference between the maximum of the last occurrences and the minimum of the first occurrences

Below is the implementation of the above approach:

C++14




// C++ program for the above approach
#include <bits/stdc++.h>
using namespace std;
 
// Function to find the length of smallest
// subarray consisting of all the occurrences
// of maximum occurring elements
int get(int arr[], int n)
{
    // Stores the frequencies
    unordered_map<int, int> occ;
 
    // Stores the maximum frequency
    int mx = -1;
 
    for (int i = 0; i < n; i++) {
        occ[arr[i]]++;
        mx = max(mx, occ[arr[i]]);
    }
 
    // Stores the maximum occurring elements
    unordered_map<int, int> chk;
 
    for (auto x : occ) {
        if (x.second == mx)
            chk[x.first]++;
    }
 
    // Stores the minimum of first occurrences
    // and maximum of last occurrences
    // of all the maximum occurring elements
    int fr = INT_MAX, sc = INT_MIN;
 
    for (int i = 0; i < n; i++) {
 
        // Maximum occurring element
        if (chk.find(arr[i]) != chk.end()) {
            fr = min(fr, i);
            sc = max(sc, i);
        }
    }
 
    return sc - fr + 1;
}
 
// Driver Code
int main()
{
    int arr[] = { 1, 2, 5, 1, 5, 5 };
    int n = sizeof(arr) / sizeof(arr[0]);
     
    cout << get(arr, n);
    return 0;
}

Java




// Java program for the above approach
import java.util.*;
 
class GFG{
 
  // Function to find the length of smallest
  // subarray consisting of all the occurrences
  // of maximum occurring elements
  static int get(int arr[], int n)
  {
 
    // Stores the frequencies
    HashMap<Integer,Integer> occ = new HashMap<Integer,Integer>();
 
    // Stores the maximum frequency
    int mx = -1;
 
    for (int i = 0; i < n; i++) {
      if(occ.containsKey(arr[i])){
        occ.put(arr[i], occ.get(arr[i])+1);
      }
      else{
        occ.put(arr[i], 1);
      }
      mx = Math.max(mx, occ.get(arr[i]));
    }
 
    // Stores the maximum occurring elements
    HashMap<Integer,Integer> chk= new HashMap<Integer,Integer>();
    for (Map.Entry<Integer,Integer> x : occ.entrySet()) {
      if (x.getValue() == mx)
        if(chk.containsKey(x.getKey())){
          chk.put(x.getKey(), chk.get(x.getKey())+1);
        }
      else{
        chk.put(x.getKey(), 1);
      }
    }
 
    // Stores the minimum of first occurrences
    // and maximum of last occurrences
    // of all the maximum occurring elements
    int fr = Integer.MAX_VALUE, sc = Integer.MIN_VALUE;
 
    for (int i = 0; i < n; i++) {
 
      // Maximum occurring element
      if (chk.containsKey(arr[i])) {
        fr = Math.min(fr, i);
        sc = Math.max(sc, i);
      }
    }
 
    return sc - fr + 1;
  }
 
  // Driver Code
  public static void main(String[] args)
  {
    int arr[] = { 1, 2, 5, 1, 5, 5 };
    int n = arr.length;
 
    System.out.print(get(arr, n));
  }
}
 
// This code is contributed by shikhasingrajput

Python3




# Python 3 program for the above approach
import sys
from collections import defaultdict
 
# Function to find the length of smallest
# subarray consisting of all the occurrences
# of maximum occurring elements
def get(arr,  n):
 
    # Stores the frequencies
    occ = defaultdict(int)
 
    # Stores the maximum frequency
    mx = -1
 
    for i in range(n):
 
        occ[arr[i]] += 1
        mx = max(mx, occ[arr[i]])
 
    # Stores the maximum occurring elements
    chk = defaultdict(int)
 
    for x in occ:
        if (occ[x] == mx):
            chk[x] += 1
 
    # Stores the minimum of first occurrences
    # and maximum of last occurrences
    # of all the maximum occurring elements
    fr = sys.maxsize
    sc = -sys.maxsize
 
    for i in range(n):
 
        # Maximum occurring element
        if (arr[i] in chk):
            fr = min(fr, i)
            sc = max(sc, i)
 
    return sc - fr + 1
 
# Driver Code
if __name__ == "__main__":
 
    arr = [1, 2, 5, 1, 5, 5]
    n = len(arr)
 
    print(get(arr, n))
 
    # This code is contributed by ukasp.

C#




// C# program for the above approach
using System;
using System.Collections;
using System.Collections.Generic;
 
class GFG
{
     
  // Function to find the length of smallest
  // subarray consisting of all the occurrences
  // of maximum occurring elements
  static int get(int []arr, int n)
  {
 
    // Stores the frequencies
    Dictionary<int, int> occ =
          new Dictionary<int, int>();
 
    // Stores the maximum frequency
    int mx = -1;
 
    for (int i = 0; i < n; i++) {
      if (occ.ContainsKey(arr[i]))
      {
        occ[arr[i]] = occ[arr[i]] + 1;
      }
      else
      {
        occ.Add(arr[i], 1);
      }
      mx = Math.Max(mx, occ[arr[i]]);
    }
    // Stores the maximum occurring elements
    Dictionary<int, int> chk =
          new Dictionary<int, int>();
           
    foreach (KeyValuePair<int, int> x in occ){
      if (x.Value == mx){
        if(chk.ContainsKey(x.Key)){
          chk[x.Key] = chk[x.Key] + 1;
        }
        else{
          chk.Add(x.Key, 1);
        }
      }
    }
 
    // Stores the minimum of first occurrences
    // and maximum of last occurrences
    // of all the maximum occurring elements
    int fr = Int32.MaxValue, sc = Int32.MinValue;
 
    for (int i = 0; i < n; i++) {
 
      // Maximum occurring element
      if (chk.ContainsKey(arr[i])) {
        fr = Math.Min(fr, i);
        sc = Math.Max(sc, i);
      }
    }
 
    return sc - fr + 1;
  }
 
  // Driver Code
  public static void Main()
  {
    int []arr = { 1, 2, 5, 1, 5, 5 };
    int n = arr.Length;
 
    Console.Write(get(arr, n));
  }
}
 
// This code is contributed by Samim Hossain Mondal.

Javascript




<script>
       // JavaScript code for the above approach
 
       // Function to find the length of smallest
       // subarray consisting of all the occurrences
       // of maximum occurring elements
       function get(arr, n)
       {
        
           // Stores the frequencies
           let occ = new Map();
 
           // Stores the maximum frequency
           let mx = -1;
 
           for (let i = 0; i < n; i++) {
 
 
               if (occ.has(arr[i])) {
                   occ.set(arr[i], occ.get(arr[i]) + 1)
               }
               else {
                   occ.set(arr[i], 1)
               }
               mx = Math.max(mx, occ.get(arr[i]));
           }
 
           // Stores the maximum occurring elements
           let chk = new Map();
 
           for (let [key, val] of occ) {
               if (val == mx)
 
                   chk.set(key, chk.get(key) + 1)
           }
 
           // Stores the minimum of first occurrences
           // and maximum of last occurrences
           // of all the maximum occurring elements
           let fr = Number.MAX_VALUE, sc = Number.MIN_VALUE;
 
           for (let i = 0; i < n; i++) {
 
               // Maximum occurring element
               if (chk.has(arr[i])) {
                   fr = Math.min(fr, i);
                   sc = Math.max(sc, i);
               }
           }
 
           return sc - fr + 1;
       }
 
       // Driver Code
       let arr = [1, 2, 5, 1, 5, 5];
       let n = arr.length;
 
       document.write(get(arr, n));
 
 // This code is contributed by Potta Lokesh
   </script>

 
 

Output
4

 

Time Complexity: O(N)
Auxiliary Space: O(N)

 


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