Reduce the array such that each element appears at most K times

Given a sorted array arr of size N, the task is to reduce the array such that each element can appear at most K times.

Examples:

Input: arr[] = {1, 2, 2, 2, 3}, K = 2
Output: {1, 2, 2, 3}
Explanation:
Remove 2 once, as it occurs more than 2 times.

Input: arr[] = {3, 3, 3}, K = 1
Output: {3}
Explanation:
Remove 3 twice, as it occurs more than 1 times.

Approach:



  1. Traverse the given array arr
  2. Maintain the count of each unique element in the array while traversing, using a pointer i
  3. If the current frequency of arr[i] till index i is less than or equal to K, add the element arr[i] to the new reduced array and increment the frequency by 1.
  4. If the current frequency of arr[i] till index i is more than K, skip till you find the next unique element.
  5. After the traversal ends, print the reduced array.

Below is the implementation of the above approach:

C++

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// C++ program to reduce the array
// such that each element appears
// at most K times
  
#include <bits/stdc++.h>
using namespace std;
  
// Function to reduce the array
void reduceArray(int arr[], int n, int K)
{
    // Vector to store the reduced array
    vector<int> vec;
    int size = 0;
    int curr_ele = arr[0], curr_freq = 1;
  
    // Iterate over the array
    for (int i = 0; i < n; i++) {
  
        if (curr_ele == arr[i]
            && curr_freq <= K) {
            vec.push_back(arr[i]);
            size++;
        }
        else if (curr_ele != arr[i]) {
            curr_ele = arr[i];
            vec.push_back(arr[i]);
            size++;
            curr_freq = 1;
        }
        curr_freq++;
    }
  
    // Print the reduced array
    cout << "{";
    for (int i = 0; i < size; i++) {
        cout << vec[i] << ", ";
    }
    cout << "}";
}
  
// Driver code
int main()
{
    int arr[]
        = { 1, 1, 1, 2,
            2, 2, 3, 3,
            3, 3, 3, 3,
            4, 5 };
  
    int n = sizeof(arr)
            / sizeof(arr[0]);
    int K = 2;
  
    // Function call
    reduceArray(arr, n, K);
  
    return 0;
}

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Java

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// Java program to reduce the array
// such that each element appears
// at most K times
import java.util.*;
  
class GFG{
   
// Function to reduce the array
static void reduceArray(int arr[], int n, int K)
{
    // Vector to store the reduced array
    Vector<Integer> vec = new Vector<Integer>();
    int size = 0;
    int curr_ele = arr[0], curr_freq = 1;
   
    // Iterate over the array
    for (int i = 0; i < n; i++) {
   
        if (curr_ele == arr[i]
            && curr_freq <= K) {
            vec.add(arr[i]);
            size++;
        }
        else if (curr_ele != arr[i]) {
            curr_ele = arr[i];
            vec.add(arr[i]);
            size++;
            curr_freq = 1;
        }
        curr_freq++;
    }
   
    // Print the reduced array
    System.out.print("{");
    for (int i = 0; i < size; i++) {
        System.out.print(vec.get(i)+ ", ");
    }
    System.out.print("}");
}
   
// Driver code
public static void main(String[] args)
{
    int arr[]
        = { 1, 1, 1, 2,
            2, 2, 3, 3,
            3, 3, 3, 3,
            4, 5 };
   
    int n = arr.length;
    int K = 2;
   
    // Function call
    reduceArray(arr, n, K);
   
}
}
  
// This code is contributed by PrinciRaj1992

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Python3

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# Python3 program to reduce the array
# such that each element appears
# at most K times
  
# Function to reduce the array
def reduceArray(arr, n, K) :
  
    # List to store the reduced array
    vec = [];
    size = 0;
    curr_ele = arr[0]; curr_freq = 1;
  
    # Iterate over the array
    for i in range(n) :
  
        if (curr_ele == arr[i]
            and curr_freq <= K) :
            vec.append(arr[i]);
            size += 1;
  
        elif (curr_ele != arr[i]) :
            curr_ele = arr[i];
            vec.append(arr[i]);
            size += 1;
            curr_freq = 1;
          
        curr_freq += 1;
  
    # Print the reduced array
    print("{",end= "");
    for i in range(size) :
        print(vec[i] ,end= ", ");
      
    print("}",end="");
  
# Driver code
if __name__ == "__main__" :
  
    arr = [ 1, 1, 1, 2,
           2, 2, 3, 3,
            3, 3, 3, 3,
            4, 5 ];
  
    n = len(arr)
    K = 2;
  
    # Function call
    reduceArray(arr, n, K);
  
# This code is contributed by AnkitRai01

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C#

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// C# program to reduce the array
// such that each element appears
// at most K times
using System;
using System.Collections.Generic;
  
class GFG{
    
// Function to reduce the array
static void reduceArray(int []arr, int n, int K)
{
    // List to store the reduced array
    List<int> vec = new List<int>();
    int size = 0;
    int curr_ele = arr[0], curr_freq = 1;
    
    // Iterate over the array
    for (int i = 0; i < n; i++) {
    
        if (curr_ele == arr[i]
            && curr_freq <= K) {
            vec.Add(arr[i]);
            size++;
        }
        else if (curr_ele != arr[i]) {
            curr_ele = arr[i];
            vec.Add(arr[i]);
            size++;
            curr_freq = 1;
        }
        curr_freq++;
    }
    
    // Print the reduced array
    Console.Write("{");
    for (int i = 0; i < size; i++) {
        Console.Write(vec[i]+ ", ");
    }
    Console.Write("}");
}
    
// Driver code
public static void Main(String[] args)
{
    int []arr
        = { 1, 1, 1, 2,
            2, 2, 3, 3,
            3, 3, 3, 3,
            4, 5 };
    
    int n = arr.Length;
    int K = 2;
    
    // Function call
    reduceArray(arr, n, K);
}
}
  
// This code is contributed by Princi Singh

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Output:

{1, 1, 2, 2, 3, 3, 4, 5, }

Time complexity: O(N)
Space complexity: O(1)

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