Find Kth Smallest and Kth Largest Element

Question

Problem: Find Kth Smallest and Kth Largest Element. Solve this hands-on electronics task on EWskills.

Accepted Answer

#include 
#include 

// Sort array in ascending order (bubble sort)
void sort_array(uint8_t *arr, uint8_t n) {
    for (uint8_t i = 0; i < n - 1; i++) {
        for (uint8_t j = 0; j < n - i - 1; j++) {
            if (arr[j] > arr[j + 1]) {
                uint8_t temp = arr[j];
                arr[j] = arr[j + 1];
                arr[j + 1] = temp;
            }
        }
    }
}

// Find kth smallest and kth largest
void find_kth_elements(uint8_t *arr, uint8_t n, uint8_t k, uint8_t *smallest, uint8_t *largest) {
    sort_array(arr, n);  // Sort the array

    *smallest = arr[k - 1];         // (k-1)th index → kth smallest
    *largest = arr[n - k];          // (n-k)th index → kth largest
}

int main() {
    uint8_t n, k;
    scanf("%hhu", &n);
    uint8_t arr[100];

    for (uint8_t i = 0; i < n; i++) {
        scanf("%hhu", &arr[i]);
    }

    scanf("%hhu", &k);

    uint8_t smallest, largest;
    find_kth_elements(arr, n, k, &smallest, &largest);

    printf("%hhu %hhu", smallest, largest);
    return 0;
}

What’s the goal?

After sorting, pick the k-1 index for kth smallest, and n-k index for kth largest.

Why it matters in firmware?

Find mid/max/threshold values in buffers (e.g., temperature ranking)
Peak detection in waveform processing
Prioritizing buffer elements without full sort in real time

Solution Logic

Use bubble sort to arrange in ascending order
Select values based on indexed position: arr[k-1] and arr[n-k]

111. Find Kth Smallest and Kth Largest Element