Find Kth Smallest and Kth Largest Element

Added some extra boundary checks

#include <stdio.h>
#include <stdint.h>

void sort_array(uint8_t *arr, uint8_t n) {
    int i,j;
    uint8_t temp;
    if(arr == NULL || n <= 1 ) return;
    for(i = 1; i < n; i++){
        temp = arr[i];
        j = i-1;
        while(j >= 0 && arr[j]>temp ){
            arr[j+1] = arr[j];
            j--;
        }
        arr[j+1] = temp;
    }
}

void find_kth_elements(uint8_t *arr, uint8_t n, uint8_t k, uint8_t *smallest, uint8_t *largest) {
    if(arr == NULL || n < 1 ) return;
    if(k <= 0 || k > n){
        *smallest = -1;
        *largest = -1;
        return;
    }
    sort_array(arr, n);
    *smallest = arr[k-1];
    *largest  = arr[n-k];
}

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;
}

Solving Approach