Number of elements less than or equal to a given number in a given subarray in C++

You are given a number and subarray lower and upper bound indexes. You need to count a number of elements that are less than or equal to the given number. Let's see an example.

Input

arr = [1, 2, 3, 4, 5, 6, 7, 8]
k = 4
lower = 0
upper = 5

Output

4

There are 4 elements between the index 0 and 5 that are less than or equal to 4.

Algorithm

• Initialise the array, number, and subarray indexes.

• Initialise the count to 0.

• Write a loop that iterates from the lower index of the subarray to the upper index of the subarray.

  • If the current element is less than or equal to the given number, then increment the count.

• Return the count.

Implementation

Following is the implementation of the above algorithm in C++

#include <bits/stdc++.h>
using namespace std;
int getElementsCount(int arr[], int n, int lower, int upper, int k) {
   if (lower < 0 || upper >= n || lower > upper) {
      return 0;
   }
   int count = 0;
   for (int i = lower; i <= upper; i++) {
      if (arr[i] <= k) {
         count += 1;
      }
   }
   return count;
}
int main() {
   int arr[] = { 1, 2, 3, 4, 5, 6, 7, 8 };
   int n = 8, k = 4;
   cout << getElementsCount(arr, n, 0, 3, k) << endl;
   cout << getElementsCount(arr, n, 4, 7, k) << endl;
   return 0;
}

Output

If you run the above code, then you will get the following result.

4
0