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Maximum possible middle element of the array after deleting exactly k elements

  • Last Updated : 05 Mar, 2021

Given an integer array of size n and a number k. If the indexing is 1 based then the middle element of the array is the element at index (n + 1) / 2, if n is odd otherwise n / 2. The task is to delete exactly k elements from the array in such a way that the middle element of the reduced array is as maximum as possible. Find the maximum possible middle element of the array after deleting exactly k elements.
Examples: 
 

Input :
n = 5, k = 2
arr[] = {9, 5, 3, 7, 10};
Output : 7

Input :
n = 9, k = 3
arr[] = {2, 4, 3, 9, 5, 8, 7, 6, 10};
Output : 9

In the first input, if we delete 5 and 3 then the array becomes {9, 7, 10} and
the middle element will be 7.
In the second input, if we delete one element before 9 and two elements after 9 
(for example 2, 5, 8) then the array becomes {4, 3, 9, 7, 6, 10} and middle 
element will be 9 and it will be the optimum solution.

 

Naive Approach : 
The naive approach is to check all possible solutions. There could be C(n, k) possible solutions. If we check all possible solutions to find an optimal solution, it will consume a lot of time. 
Optimal Approach : 
After deleting k elements, the array will be reduced to size n – k. Since we can delete any k numbers from the array to find the maximum possible middle elements. If we note, the index of the middle element after deleting k elements will lie in the range ( n + 1 – k ) / 2 and ( n + 1 – k ) / 2 + k. So in order to find the optimal solution, simply iterate the array from the index ( n + 1 – k ) / 2 to index ( n + 1 – k ) / 2 + k and select the maximum element in this range. 
The is the implementation is given below. 
 

C++




#include <bits/stdc++.h>
using namespace std;
 
// Function to calculate maximum possible middle
// value of the array after deleting exactly k
// elements
int maximum_middle_value(int n, int k, int arr[])
{
    // Initialize answer as -1
    int ans = -1;
 
    // Calculate range of elements that can give
    // maximum possible middle value of the array
    // since index of maximum possible middle
    // value after deleting exactly k elements from
    // array will lie in between low and high
    int low = (n + 1 - k) / 2;
 
    int high = (n + 1 - k) / 2 + k;
 
    // Find maximum element of the array in
    // range low and high
    for (int i = low; i <= high; i++) {
 
        // since indexing is 1 based so
        // check element at index i - 1
        ans = max(ans, arr[i - 1]);
    }
 
    // Return the maximum possible middle value
    //  of the array after deleting exactly k
    // elements from the array
    return ans;
}
 
// Driver Code
int main()
{
    int n = 5, k = 2;
    int arr[] = { 9, 5, 3, 7, 10 };
    cout << maximum_middle_value(n, k, arr) << endl;
 
    n = 9;
    k = 3;
    int arr1[] = { 2, 4, 3, 9, 5, 8, 7, 6, 10 };
    cout << maximum_middle_value(n, k, arr1) << endl;
 
    return 0;
}

Java




// Java implementation of the approach
import java.util.*;
 
class GFG
{
 
// Function to calculate maximum possible middle
// value of the array after deleting exactly k
// elements
static int maximum_middle_value(int n, int k, int arr[])
{
    // Initialize answer as -1
    int ans = -1;
 
    // Calculate range of elements that can give
    // maximum possible middle value of the array
    // since index of maximum possible middle
    // value after deleting exactly k elements from
    // array will lie in between low and high
    int low = (n + 1 - k) / 2;
 
    int high = (n + 1 - k) / 2 + k;
 
    // Find maximum element of the array in
    // range low and high
    for (int i = low; i <= high; i++)
    {
 
        // since indexing is 1 based so
        // check element at index i - 1
        ans = Math.max(ans, arr[i - 1]);
    }
 
    // Return the maximum possible middle value
    // of the array after deleting exactly k
    // elements from the array
    return ans;
}
 
// Driver Code
public static void main(String args[])
{
    int n = 5, k = 2;
    int arr[] = { 9, 5, 3, 7, 10 };
    System.out.println( maximum_middle_value(n, k, arr));
 
    n = 9;
    k = 3;
    int arr1[] = { 2, 4, 3, 9, 5, 8, 7, 6, 10 };
    System.out.println( maximum_middle_value(n, k, arr1));
}
}
 
// This code is contributed by Arnab Kundu

Python3




# Python3 implementation of the approach
 
# Function to calculate maximum possible
# middle value of the array after
# deleting exactly k elements
def maximum_middle_value(n, k, arr):
  
    # Initialize answer as -1
    ans = -1
 
    # Calculate range of elements that can give
    # maximum possible middle value of the array
    # since index of maximum possible middle
    # value after deleting exactly k elements
    # from array will lie in between low and high
    low = (n + 1 - k) // 2
 
    high = (n + 1 - k) // 2 + k
 
    # Find maximum element of the
    # array in range low and high
    for i in range(low, high+1): 
 
        # since indexing is 1 based so
        # check element at index i - 1
        ans = max(ans, arr[i - 1])
      
    # Return the maximum possible middle
    # value of the array after deleting
    # exactly k elements from the array
    return ans
  
# Driver Code
if __name__ == "__main__":
  
    n, k = 5, 2
    arr = [9, 5, 3, 7, 10]
    print(maximum_middle_value(n, k, arr))
 
    n, k = 9, 3
    arr1 = [2, 4, 3, 9, 5, 8, 7, 6, 10
    print(maximum_middle_value(n, k, arr1))
 
# This code is contributed by Rituraj Jain

C#




// C# implementation of the approach
using System;
 
class GFG
{
     
// Function to calculate maximum possible middle
// value of the array after deleting exactly k
// elements
static int maximum_middle_value(int n, int k, int []arr)
{
    // Initialize answer as -1
    int ans = -1;
 
    // Calculate range of elements that can give
    // maximum possible middle value of the array
    // since index of maximum possible middle
    // value after deleting exactly k elements from
    // array will lie in between low and high
    int low = (n + 1 - k) / 2;
 
    int high = (n + 1 - k) / 2 + k;
 
    // Find maximum element of the array in
    // range low and high
    for (int i = low; i <= high; i++)
    {
 
        // since indexing is 1 based so
        // check element at index i - 1
        ans = Math.Max(ans, arr[i - 1]);
    }
 
    // Return the maximum possible middle value
    // of the array after deleting exactly k
    // elements from the array
    return ans;
}
 
// Driver Code
static public void Main ()
{
         
    int n = 5, k = 2;
    int []arr = { 9, 5, 3, 7, 10 };
    Console.WriteLine( maximum_middle_value(n, k, arr));
 
    n = 9;
    k = 3;
    int []arr1 = { 2, 4, 3, 9, 5, 8, 7, 6, 10 };
    Console.WriteLine( maximum_middle_value(n, k, arr1));
}
}
 
// This code is contributed by ajit.

Javascript




<script>
 
// Function to calculate maximum possible middle
// value of the array after deleting exactly k
// elements
function maximum_middle_value(n, k, arr)
{
    // Initialize answer as -1
    let ans = -1;
 
    // Calculate range of elements that can give
    // maximum possible middle value of the array
    // since index of maximum possible middle
    // value after deleting exactly k elements from
    // array will lie in between low and high
    let low = Math.floor((n + 1 - k) / 2);
 
    let high = Math.floor(((n + 1 - k) / 2) + k);
 
    // Find maximum element of the array in
    // range low and high
    for (let i = low; i <= high; i++) {
 
        // since indexing is 1 based so
        // check element at index i - 1
        ans = Math.max(ans, arr[i - 1]);
    }
 
    // Return the maximum possible middle value
    // of the array after deleting exactly k
    // elements from the array
    return ans;
}
 
// Driver Code
 
    let n = 5, k = 2;
    let arr = [ 9, 5, 3, 7, 10 ];
    document.write(maximum_middle_value(n, k, arr) + "<br>");
 
    n = 9;
    k = 3;
    let arr1 = [ 2, 4, 3, 9, 5, 8, 7, 6, 10 ];
    document.write(maximum_middle_value(n, k, arr1) + "<br>");
 
 
// This code is contributed by Mayank Tyagi
 
</script>
Output: 
7
9

 




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