Maximize minimum distance between repetitions from any permutation of the given Array

Given an array arr[], consisting of N positive integers in the range [1, N], the task is to find the largest minimum distance between any consecutive repetition of an element from any permutation of the given array.

Examples:

Input: arr[] = {1, 2, 1, 3} 
Output:
Explanation: The maximum possible distance between the repetition is 3, from the permutation {1, 2, 3, 1} or {1, 3, 2, 1}.
Input: arr[] = {1, 2, 3, 4} 
Output: 0

Approach: Follow the steps below to solve the problem:  

  1. Store the frequency of each array element.
  2. Find the element which contains the maximum frequency, say maxFreqElement.
  3. Count the number of occurrences of elements having a maximum frequency, say maxFreqCount.
  4. Calculate the required distance by the equation (N- maxFreqCount)/( maxFreqElement- 1))

Below is the implementation of the above approach.



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// C++ Program to implement 
// the above approach 
#include <bits/stdc++.h> 
using namespace std; 
int findMaxLen(vector<int>& a) 
  
    // Size of the array 
    int n = a.size(); 
  
    // Stores the frequency of 
    // array elements 
    int freq[n + 1]; 
    memset(freq, 0, sizeof freq); 
  
    for (int i = 0; i < n; ++i) { 
        freq[a[i]]++; 
    
  
    int maxFreqElement = INT_MIN; 
    int maxFreqCount = 1; 
  
    for (int i = 1; i <= n; ++i) { 
  
        // Find the highest frequency 
        // in the array 
        if (freq[i] > maxFreqElement) { 
            maxFreqElement = freq[i]; 
            maxFreqCount = 1; 
        
  
        // Increase count of max frequent element 
        else if (freq[i] == maxFreqElement) 
            maxFreqCount++; 
    
  
    int ans; 
  
    // If no repetition is present 
    if (maxFreqElement == 1) 
        ans = 0; 
    else
        // Find the maximum distance 
        ans = ((n - maxFreqCount) 
            / (maxFreqElement - 1)); 
    
  
    // Return the max distance 
    return ans; 
  
// Driver Code 
int main() 
  
    vector<int> a = { 1, 2, 1, 2 }; 
    cout << findMaxLen(a) << endl; 
  
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// Java program to implement 
// the above approach 
class GFG{
      
static int findMaxLen(int a[], int n) 
      
    // Stores the frequency of 
    // array elements 
    int freq[] = new int[n + 1]; 
  
    for(int i = 0; i < n; ++i)
    
        freq[a[i]]++; 
    
  
    int maxFreqElement = Integer.MIN_VALUE; 
    int maxFreqCount = 1
  
    for(int i = 1; i <= n; ++i)
    
          
        // Find the highest frequency 
        // in the array 
        if (freq[i] > maxFreqElement)
        
            maxFreqElement = freq[i]; 
            maxFreqCount = 1
        
  
        // Increase count of max frequent element 
        else if (freq[i] == maxFreqElement) 
            maxFreqCount++; 
    
  
    int ans; 
  
    // If no repetition is present 
    if (maxFreqElement == 1
        ans = 0
    else 
    {
          
        // Find the maximum distance 
        ans = ((n - maxFreqCount) / 
               (maxFreqElement - 1)); 
    
  
    // Return the max distance 
    return ans; 
  
// Driver Code 
public static void main(String [] args) 
    int a[] = { 1, 2, 1, 2 }; 
    int n = a.length;
      
    System.out.print(findMaxLen(a, n));
}
}
  
// This code is contributed by chitranayal
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# Python3 program to implement
# the above approach
import sys
  
def findMaxLen(a):
  
    # Size of the array
    n = len(a)
  
    # Stores the frequency of
    # array elements
    freq = [0] * (n + 1)
  
    for i in range(n):
        freq[a[i]] += 1
  
    maxFreqElement = -sys.maxsize - 1
    maxFreqCount = 1
  
    for i in range(1, n + 1):
  
        # Find the highest frequency
        # in the array
        if(freq[i] > maxFreqElement):
            maxFreqElement = freq[i]
            maxFreqCount = 1
  
        # Increase count of max frequent element
        elif(freq[i] == maxFreqElement):
            maxFreqCount += 1
  
    # If no repetition is present
    if(maxFreqElement == 1):
        ans = 0
    else:
          
        # Find the maximum distance
        ans = ((n - maxFreqCount) // 
               (maxFreqElement - 1))
  
    # Return the max distance
    return ans
  
# Driver Code
a = [ 1, 2, 1, 2 ]
  
# Function call
print(findMaxLen(a))
  
# This code is contributed by Shivam Singh
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// C# program to implement
// the above approach
using System;
class GFG{
  
    static int findMaxLen(int[] a, int n)
    {
  
        // Stores the frequency of
        // array elements
        int[] freq = new int[n + 1];
  
        for (int i = 0; i < n; ++i) 
        {
            freq[a[i]]++;
        }
      
        int maxFreqElement = int.MinValue;
        int maxFreqCount = 1;
      
        for (int i = 1; i <= n; ++i) 
        {
  
            // Find the highest frequency
            // in the array
            if (freq[i] > maxFreqElement) 
            {
                maxFreqElement = freq[i];
                maxFreqCount = 1;
            }
  
            // Increase count of max 
            // frequent element
            else if (freq[i] == maxFreqElement)
                maxFreqCount++;
        }
  
        int ans;
  
        // If no repetition is present
        if (maxFreqElement == 1)
            ans = 0;
        else
        {
  
            // Find the maximum distance
            ans = ((n - maxFreqCount) / 
                   (maxFreqElement - 1));
        }
  
        // Return the max distance
        return ans;
    }
  
    // Driver Code
    public static void Main(String[] args)
    {
        int[] a = {1, 2, 1, 2};
        int n = a.Length;
        Console.Write(findMaxLen(a, n));
    }
}
  
// This code is contributed by Amit Katiyar
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Output: 
2


 

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

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