Count How Many Readings Exceed a Threshold

Title: Count Values Above Threshold
Level: Easy
Concepts: for loop, array traversal, boundary checks, counters, input validation

Scenario

A small data-logger collects sensor samples (integers). Your task is to scan the array and count how many readings exceed a given threshold. Since the array length may vary, a clean and simple for loop must be used to iterate through all elements and compute the count.

Problem Statement

Implement a function that counts how many elements in an integer array are strictly greater than a given threshold using a basic for loop`. The function must validate inputs and return an error if any pointer is invalid or array size is negative.

Requirements

• Use only a standard for loop` for iteration.
• Inputs:
  • a[] — integer array
  • n — number of elements (may be 0 or more)
  • threshold — reference value
• Output:
  • *out_count — number of elements strictly greater than threshold
• Error handling:
  • If a == NULL or out_count == NULL or n < 0 → return error (-1)
  • On error: do not modify *out_count

Function Details

• Name: count_above_threshold
• Arguments:
  • const int *a
  • int n
  • int threshold
  • int *out_count
• Return Value:
  • int — 0 on success, -1 on invalid input.
• Description:
  The function should loop from index 0 to n-1 using a for (i=0; i<n; i++) pattern, compare each element with threshold, and increment a local counter.

Solution Approach

• Validate inputs.
• Initialize a local variable count = 0;
• Use a classic for-loop:
• Store the result into *out_count and return success.

Tasks to Perform

1. Validate:
   • a != NULL
   • out_count != NULL
   • n >= 0
2. Initialize count = 0
3. Iterate using a for loop and count values strictly greater than threshold
4. Store the result in *out_count
5. Return 0
6. On invalid input, return -1 and do not write to output

Test Cases