Count subarrays with all elements greater than K

Given an array of N integers and a number K, the task is to find the number of subarrays such that all elements are greater than K in it.

Examples:

Input: a[] = {3, 4, 5, 6, 7, 2, 10, 11}, K = 5
Output: 6
The possible subarrays are {6}, {7}, {6, 7}, {10}, {11} and {10, 11}.



Input: a[] = {8, 25, 10, 19, 19, 18, 20, 11, 18}, K = 13
Output: 12

Approach: The idea is to start traversing the array using a counter. If the current element is greater than the given value X, increment the counter otherwise add counter*(counter+1)/2 to the number of subarrays and reinitialize counter to 0.

Below is the implementation of the above approach:

C++

filter_none

edit
close

play_arrow

link
brightness_4
code

// C++ program to print the number of subarrays such
// that all elements are greater than K
#include <bits/stdc++.h>
using namespace std;
  
// Function to count number of subarrays
int countSubarrays(int a[], int n, int x)
{
    int count = 0;
  
    int number = 0;
  
    // Iterate in the array
    for (int i = 0; i < n; i++) {
  
        // check if array element
        // greater then X or not
        if (a[i] > x) {
            count += 1;
        }
        else {
  
            number += (count) * (count + 1) / 2;
            count = 0;
        }
    }
  
    // After iteration complete
    // check for the last set of subarrays
    if (count)
        number += (count) * (count + 1) / 2;
  
    return number;
}
  
// Driver Code
int main()
{
    int a[] = { 3, 4, 5, 6, 7, 2, 10, 11 };
    int n = sizeof(a) / sizeof(a[0]);
    int k = 5;
  
    cout << countSubarrays(a, n, k);
  
    return 0;
}

chevron_right


Java

filter_none

edit
close

play_arrow

link
brightness_4
code

// Java program to print the number of subarrays such 
// that all elements are greater than K 
  
import java.io.*;
  
class GFG {
      
// Function to count number of subarrays 
static int countSubarrays(int a[], int n, int x) 
    int count = 0
  
    int number = 0
  
    // Iterate in the array 
    for (int i = 0; i < n; i++) { 
  
        // check if array element 
        // greater then X or not 
        if (a[i] > x) { 
            count += 1
        
        else
  
            number += (count) * (count + 1) / 2
            count = 0
        
    
  
    // After iteration complete 
    // check for the last set of subarrays 
    if (count!=0
        number += (count) * (count + 1) / 2
  
    return number; 
  
// Driver Code 
    public static void main (String[] args) {
        int a[] = { 3, 4, 5, 6, 7, 2, 10, 11 }; 
        int n = a.length; 
        int k = 5
  
        System.out.println (countSubarrays(a, n, k)); 
          
    }
}

chevron_right


Python3

filter_none

edit
close

play_arrow

link
brightness_4
code

# Python program to print the number of 
# subarrays such that all elements are 
# greater than K
  
# Function to count number of subarrays
def countSubarrays(a, n, x):
    count = 0
    number = 0
      
    # Iterate in the array
    for i in range(n):
          
        # check if array element greater
        # then X or not
        if (a[i] > x):
            count += 1
        else:
            number += (count) * (count + 1) / 2
            count = 0
              
    # After iteration complete check for
    # the last set of subarrays
    if (count):
        number += (count) * (count + 1) / 2
    return int(number)
  
# Driver Code
if __name__ == '__main__':
    a = [3, 4, 5, 6, 7, 2, 10, 11]
    n = len(a)
    k = 5
    print(countSubarrays(a, n, k))
  
# This code is contributed by 29AjayKumar

chevron_right


C#

filter_none

edit
close

play_arrow

link
brightness_4
code

// C# program to print the number of subarrays such 
// that all elements are greater than K 
  
using System;
  
class GFG {
      
// Function to count number of subarrays 
static int countSubarrays(int []a, int n, int x) 
    int count = 0; 
  
    int number = 0; 
  
    // Iterate in the array 
    for (int i = 0; i < n; i++) { 
  
        // check if array element 
        // greater then X or not 
        if (a[i] > x) { 
            count += 1; 
        
        else
  
            number += (count) * (count + 1) / 2; 
            count = 0; 
        
    
  
    // After iteration complete 
    // check for the last set of subarrays 
    if (count!=0) 
        number += (count) * (count + 1) / 2; 
  
    return number; 
  
// Driver Code 
    public static void Main () {
        int []a = { 3, 4, 5, 6, 7, 2, 10, 11 }; 
        int n = a.Length; 
        int k = 5; 
  
        Console.WriteLine(countSubarrays(a, n, k)); 
          
    }
}
// This code is contributed by anuj_67..

chevron_right


PHP

filter_none

edit
close

play_arrow

link
brightness_4
code

<?php
// PHP program to print the number 
// of subarrays such that all 
// elements are greater than K
  
// Function to count number 
// of subarrays
function countSubarrays($a, $n, $x)
{
    $count = 0; $number = 0;
  
    // Iterate in the array
    for ($i = 0; $i < $n; $i++) 
    {
  
        // check if array element
        // greater then X or not
        if ($a[$i] > $x)
        {
            $count += 1;
        }
        else 
        {
            $number += ($count) * 
                       ($count + 1) / 2;
            $count = 0;
        }
    }
  
    // After iteration complete
    // check for the last set
    // of subarrays
    if ($count)
        $number += ($count) *
                   ($count + 1) / 2;
  
    return $number;
}
  
// Driver Code
$a = array(3, 4, 5, 6, 7, 2, 10, 11);
$n = count($a);
$k = 5;
  
echo countSubarrays($a, $n, $k);
  
// This code is contributed by anuj_67
?>

chevron_right


Output:

6

Time Complexity: O(N)
Auxiliary Space: O(1)



My Personal Notes arrow_drop_up

Striver(underscore)79 at Codechef and codeforces D

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.



Improved By : jit_t, vt_m, 29AjayKumar



Article Tags :
Practice Tags :


1


Please write to us at contribute@geeksforgeeks.org to report any issue with the above content.