Sample Code

GitHub link - UPDATE WITH LINK TO SOLUTION CODE IN REPO

#include <assert.h>
#include <ctype.h>
#include <limits.h>
#include <math.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
char* readline();
char* ltrim(char*);
char* rtrim(char*);
int parse_int(char*);
typedef struct SinglyLinkedListNode SinglyLinkedListNode;
typedef struct SinglyLinkedList SinglyLinkedList;
struct SinglyLinkedListNode {
    int data;
    SinglyLinkedListNode* next;
};
struct SinglyLinkedList {
    SinglyLinkedListNode* head;
    SinglyLinkedListNode* tail;
};
SinglyLinkedListNode* create_singly_linked_list_node(int node_data) {
    SinglyLinkedListNode* node = malloc(sizeof(SinglyLinkedListNode));
    node->data = node_data;
    node->next = NULL;
    return node;
}
void insert_node_into_singly_linked_list(SinglyLinkedList** singly_linked_list, int node_data) {
    SinglyLinkedListNode* node = create_singly_linked_list_node(node_data);
    if (!(*singly_linked_list)->head) {
        (*singly_linked_list)->head = node;
    } else {
        (*singly_linked_list)->tail->next = node;
    }
    (*singly_linked_list)->tail = node;
}
void print_singly_linked_list(SinglyLinkedListNode* node, char* sep, FILE* fptr) {
    while (node) {
        fprintf(fptr, "%d", node->data);
        node = node->next;
        if (node) {
            fprintf(fptr, "%s", sep);
        }
    }
}
/**********************************************************************************************************************/
// Ignore everything above here
/*
 * Complete the 'findMark' function below.
 *
 * The function is expected to return an INTEGER.
 * The function accepts following parameters:
 *  1. INTEGER rank
 *  2. INTEGER_SINGLY_LINKED_LIST marks
 */
/*
 * For your reference:
 *
 * SinglyLinkedListNode {
 *     int data;
 *     SinglyLinkedListNode* next;
 * };
 *
 */
int findMark(int rank, SinglyLinkedListNode* marks) {
    // Creating a pointer to keep track of the start of the linked list
    SinglyLinkedListNode *head = marks;
    
    // Counting how many nodes are in the linked list so we know how large to make our array
    int n = 0;
    while (marks != NULL) {
        n++;
        marks = marks->next;
    }
    
    // Putting all our mark values into an array so we can sort it easier later
    marks = head;
    int idx = 0;
    int marksArray[n];
    while (marks != NULL) {
        marksArray[idx] = marks->data;
        idx++;
        marks = marks->next;
    }
    
    // Creating a second array with the marked sorted
    int sortedMarks[n];
    int i = 0;
    while (i < n) {
        int currMax = 0;
        int currMaxIdx = 0;
        int j = 0;
        while (j < n) {
            if (marksArray[j] > currMax) {
                currMax = marksArray[j];
                currMaxIdx = j;
            }
            j++;
        }
        sortedMarks[i] = currMax;
        marksArray[currMaxIdx] = -1;
        i++;
    }
    
    // Returning the mark of the given rank
    // Since the marks are sorted, we can just send back the element at the index of the rank 
    // (minus 1 because arrays start at index 0)
    return sortedMarks[rank - 1];
}
// Ignore everything below here
/**********************************************************************************************************************/
int main()
{
    FILE* fptr = fopen(getenv("OUTPUT_PATH"), "w");
    int n = parse_int(ltrim(rtrim(readline())));
    SinglyLinkedList* l = malloc(sizeof(SinglyLinkedList));
    l->head = NULL;
    l->tail = NULL;
    int l_count = parse_int(ltrim(rtrim(readline())));
    for (int i = 0; i < l_count; i++) {
        int l_item = parse_int(ltrim(rtrim(readline())));
        insert_node_into_singly_linked_list(&l, l_item);
    }
    int result = findMark(n, l->head);
    fprintf(fptr, "%d\n", result);
    fclose(fptr);
    return 0;
}
char* readline() {
    size_t alloc_length = 1024;
    size_t data_length = 0;
    char* data = malloc(alloc_length);
    while (true) {
        char* cursor = data + data_length;
        char* line = fgets(cursor, alloc_length - data_length, stdin);
        if (!line) {
            break;
        }
        data_length += strlen(cursor);
        if (data_length < alloc_length - 1 || data[data_length - 1] == '\n') {
            break;
        }
        alloc_length <<= 1;
        data = realloc(data, alloc_length);
        if (!data) {
            data = '\0';
            break;
        }
    }
    if (data[data_length - 1] == '\n') {
        data[data_length - 1] = '\0';
        data = realloc(data, data_length);
        if (!data) {
            data = '\0';
        }
    } else {
        data = realloc(data, data_length + 1);
        if (!data) {
            data = '\0';
        } else {
            data[data_length] = '\0';
        }
    }
    return data;
}
char* ltrim(char* str) {
    if (!str) {
        return '\0';
    }
    if (!*str) {
        return str;
    }
    while (*str != '\0' && isspace(*str)) {
        str++;
    }
    return str;
}
char* rtrim(char* str) {
    if (!str) {
        return '\0';
    }
    if (!*str) {
        return str;
    }
    char* end = str + strlen(str) - 1;
    while (end >= str && isspace(*end)) {
        end--;
    }
    *(end + 1) = '\0';
    return str;
}
int parse_int(char* str) {
    char* endptr;
    int value = strtol(str, &endptr, 10);
    if (endptr == str || *endptr != '\0') {
        exit(EXIT_FAILURE);
    }
    return value;
}