Find the number of elements greater than k in a sorted array

Given a sorted array arr[] of integers and an integer k, the task is to find the count of elements in the array which are greater than k. Note that k may or may not be present in the array.

Examples:

Input: arr[] = {2, 3, 5, 6, 6, 9}, k = 6
Output: 1

Input: arr[] = {1, 1, 2, 5, 5, 7}, k = 8
Output: 0

Approach: The idea is to perform binary search and find the number of elements greater than k.

Below is the implementation of the above approach:

filter_none

edit
close

play_arrow

link
brightness_4
code

// C++ implementation of the approach
#include <bits/stdc++.h>
using namespace std;
  
// Function to return the count of elements
// from the array which are greater than k
int countGreater(int arr[], int n, int k)
{
    int l = 0;
    int r = n - 1;
  
    // Stores the index of the left most element
    // from the array which is greater than k
    int leftGreater = n;
  
    // Finds number of elements greater than k
    while (l <= r) {
        int m = l + (r - l) / 2;
  
        // If mid element is greater than
        // k update leftGreater and r
        if (arr[m] > k) {
            leftGreater = m;
            r = m - 1;
        }
  
        // If mid element is less than
        // or equal to k update l
        else
            l = m + 1;
    }
  
    // Return the count of elements greater than k
    return (n - leftGreater);
}
  
// Driver code
int main()
{
    int arr[] = { 3, 3, 4, 7, 7, 7, 11, 13, 13 };
    int n = sizeof(arr) / sizeof(arr[0]);
  
    int k = 7;
  
    cout << countGreater(arr, n, k);
  
    return 0;
}
chevron_right

filter_none

edit
close

play_arrow

link
brightness_4
code

// Java implementation of the approach
class GFG
{
      
// Function to return the count of elements
// from the array which are greater than k
static int countGreater(int arr[], int n, int k)
{
    int l = 0;
    int r = n - 1;
  
    // Stores the index of the left most element
    // from the array which is greater than k
    int leftGreater = n;
  
    // Finds number of elements greater than k
    while (l <= r) {
        int m = l + (r - l) / 2;
  
        // If mid element is greater than
        // k update leftGreater and r
        if (arr[m] > k) {
            leftGreater = m;
            r = m - 1;
        }
  
        // If mid element is less than
        // or equal to k update l
        else
            l = m + 1;
    }
  
    // Return the count of elements greater than k
    return (n - leftGreater);
}
  
// Driver code
public static void main(String[] args)
{
    int arr[] = { 3, 3, 4, 7, 7, 7, 11, 13, 13 };
    int n = arr.length;
  
    int k = 7;
  
    System.out.println(countGreater(arr, n, k));
}
}
  
// This code is contributed by Code_Mech
chevron_right

filter_none

edit
close

play_arrow

link
brightness_4
code

# Python 3 implementation of the approach
  
# Function to return the count of elements
# from the array which are greater than k
def countGreater(arr, n, k):
    l = 0
    r = n - 1
  
    # Stores the index of the left most element
    # from the array which is greater than k
    leftGreater = n
  
    # Finds number of elements greater than k
    while (l <= r):
        m = int(l + (r - l) / 2)
  
        # If mid element is greater than
        # k update leftGreater and r
        if (arr[m] > k):
            leftGreater = m
            r = m - 1
  
        # If mid element is less than
        # or equal to k update l
        else:
            l = m + 1
  
    # Return the count of elements 
    # greater than k
    return (n - leftGreater)
  
# Driver code
if __name__ == '__main__':
    arr = [3, 3, 4, 7, 7, 7, 11, 13, 13]
    n = len(arr)
    k = 7
  
    print(countGreater(arr, n, k))
# This code is contributed by
# Surendra_Gangwar
chevron_right

filter_none

edit
close

play_arrow

link
brightness_4
code

// C# implementation of the approach
using System;
  
class GFG
{
      
// Function to return the count of elements
// from the array which are greater than k
static int countGreater(int[]arr, int n, int k)
{
    int l = 0;
    int r = n - 1;
  
    // Stores the index of the left most element
    // from the array which is greater than k
    int leftGreater = n;
  
    // Finds number of elements greater than k
    while (l <= r) 
    {
        int m = l + (r - l) / 2;
  
        // If mid element is greater than
        // k update leftGreater and r
        if (arr[m] > k) 
        {
            leftGreater = m;
            r = m - 1;
        }
  
        // If mid element is less than
        // or equal to k update l
        else
            l = m + 1;
    }
  
    // Return the count of elements greater than k
    return (n - leftGreater);
}
  
// Driver code
public static void Main()
{
    int[] arr = { 3, 3, 4, 7, 7, 7, 11, 13, 13 };
    int n = arr.Length;
  
    int k = 7;
  
    Console.WriteLine(countGreater(arr, n, k));
}
}
  
// This code is contributed by Code_Mech
chevron_right

filter_none

edit
close

play_arrow

link
brightness_4
code

<?php
// PHP implementation of the approach
  
// Function to return the count of elements
// from the array which are greater than k
function countGreater($arr, $n, $k)
{
    $l = 0;
    $r = $n - 1;
  
    // Stores the index of the left most element
    // from the array which is greater than k
    $leftGreater = $n;
  
    // Finds number of elements greater than k
    while ($l <= $r
    {
        $m = $l + (int)(($r - $l) / 2);
  
        // If mid element is greater than
        // k update leftGreater and r
        if ($arr[$m] > $k
        {
            $leftGreater = $m;
            $r = $m - 1;
        }
  
        // If mid element is less than
        // or equal to k update l
        else
            $l = $m + 1;
    }
  
    // Return the count of elements greater than k
    return ($n - $leftGreater);
}
  
// Driver code
$arr = array(3, 3, 4, 7, 7, 7, 11, 13, 13);
$n = sizeof($arr);
$k = 7;
  
echo countGreater($arr, $n, $k);
  
// This code is contributed
// by Akanksha Rai
chevron_right

Output:
3

Time Complexity: O(log(n)) where n is the number of elements in the array.




Check out this Author's contributed articles.

If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.





Article Tags :